Large magnetic entropy change(△S_(M))can realize a prominent heat transformation under the magnetic field and directly strengthen the efficacy of the magnetocaloric effect,which provides a pioneering environmentally ...Large magnetic entropy change(△S_(M))can realize a prominent heat transformation under the magnetic field and directly strengthen the efficacy of the magnetocaloric effect,which provides a pioneering environmentally friendly solidstate strategy to improve refrigeration capacities and efficiencies.The second-order magnetic transition(SOMT)materials have broader△S_(M) peaks without thermal hysteresis,making them highly attractive in magnetic refrigeration,especially in the room temperature range.Here,we report a significant enhancement of△S_(M) at room temperature in single-crystal Mn_(5)Ge_(3).In this SOMT system,we realize a 60%improvement of-△S_(M)^(max) from 3.5 J/kg·K to 5.6 J/kg·K at T=300 K.This considerable enhancement of△S_(M) is achieved by intentionally introducing strain energy through high-pressure constrained deformation.Both experimental results and Monte Carlo simulations demonstrate that the enhancement of△S_(M) originates from the microscopic strain and lattice deformation induced by strain energy after deformation.This strain energy will reconstruct the energy landscape of this ferromagnetic system and enhance magnetization,resulting in a giant intensity of magnetocaloric responses.Our findings provide an approach to increase magnetic entropy change and may give fresh ideas for exploring advanced magnetocaloric materials.展开更多
Rising global temperatures alongside increasing energy demand highlight the imperative for sustainable and energy-efficient refrigeration technologies.Magnetic refrigeration,based on the magnetocaloric effect(MCE),pre...Rising global temperatures alongside increasing energy demand highlight the imperative for sustainable and energy-efficient refrigeration technologies.Magnetic refrigeration,based on the magnetocaloric effect(MCE),presents a compelling solid-state alternative to traditional vapor-compression systems.However,many high-performance magnetocaloric materials rely on critical elements such as rare earths,cobalt and germanium.Despite extensive compositional flexibility,high-entropy alloys(HEAs)have predominantly been investigated in equiatomic compositions incorporating significant quantities of highly critical elements to achieve large MCE or mixing rare-earth elements in majority proportions that only yield moderate MCE values,thereby failing to address issues of material criticality.In this study,we present a criticality-aware design strategy for the MnNiSi-HEA system,exemplifying a prototype of the latest third-generation HEAs.Various substitutional approaches were evaluated to achieve the coupling between magnetic and structural transitions.The most effective pathway,identified through the co-substitution of Fe and Cu reduces the structural transition temperature by over 900 K relative to MnNiSi while preserving the ferromagnetic characteristics of the low-temperature phase,successfully inducing a first-order magnetostructural transformation near room temperature.The resulting alloys,Mn_(0.5)Fe_(0.5)Ni_(1−x)Cu_(x)Si,exhibit coupled transitions spanning more than 100 K and demonstrate the highest MCE reported to date among HEAs free of cobalt,germanium and rare-earth elements,outperforming previous records by 360%.Complementary density functional theory calculations confirm the stability of the orthorhombic and hexagonal phases.Predictions of lattice entropy change closely match calorimetric measurements.This study establishes a new benchmark for low-criticality magnetocaloric HEAs,underscoring that optimal functional performance and sustainable material development can be achieved concomitantly.The proposed design methodology offers a valuable framework for advancing resource-resilient solid-state cooling materials and underscores the potential of HEAs as a platform for sustainable functional materials.展开更多
High-entropy magnetocaloric alloys offer exceptional compositional flexibility and stability for magnetic refrigeration.However,enhancing their magnetic entropy change,working temperature range,and refrigeration capac...High-entropy magnetocaloric alloys offer exceptional compositional flexibility and stability for magnetic refrigeration.However,enhancing their magnetic entropy change,working temperature range,and refrigeration capacity remains challenging.In this study,we demonstrate that microalloying GdTbDyHo with only 0.4at%nonmagnetic Y effectively addresses this limitation.Our analysis indicates that Y uniformly dissolves into the hexagonal matrix lattice,disrupting the 4f–4f exchange interactions and inducing a local short-range order.This weakens the antiferromagnetic coupling,accelerates the antiferromagnetic–ferromagnetic transition,and broadensits range.Consequently,the peak magnetic entropy change increases from 8.2 to 8.7 J·kg^(−1)·K^(−1),the working temperature range expands from 77 to 89 K,and the refrigeration capacity improves by 23%,reaching 774 J·kg^(−1)(5 T)relative to the Y-free alloy,while the Néel temperature remains constant(~195 K).This study establishes nonmagnetic microalloying as a cost-effective and scalable strategy for designing high-performance magnetocaloric materials.展开更多
Rare-earth based frustrated magnets have attracted great attention as excellent candidates for magnetic refrigeration at sub-Kelvin temperatures,while the experimental identification of systems exhibiting both large v...Rare-earth based frustrated magnets have attracted great attention as excellent candidates for magnetic refrigeration at sub-Kelvin temperatures,while the experimental identification of systems exhibiting both large volumetric cooling capacity and reduced working temperatures far below 1K remains a challenge.Here,through ultra-low temperature magnetism and thermodynamic characterizations,we unveil the large magnetocaloric effect(MCE)realized at sub-Kelvin temperatures in the frustrated Kagome antiferromagnet Gd_(3)BWO_(9) with T_(N)∼1.0 K.The isothermal magnetization curves indicate the existence of field(B)induced anisotropic magnetic phase diagrams,where four distinct magnetic phases for B‖c-axis and five magnetic phases for B‖ab-plane are identified at T<T_(N).The analysis of magnetic entropy S(B,T)data and direct adiabatic demagnetization tests reveal remarkable cooling performance at sub-Kelvin temperatures featured by a large volumetric entropy density of 502.2 mJ/K/cm^(3)and a low attainable minimal temperature T_(min)∼168mK from the initial cooling condition of 2K and 6 T,surpassing most Gd-based refrigerants previously documented in temperature ranges of 0.25–4 K.The realized T_(min)∼168mK far below T_(N)∼1.0K in Gd_(3)BWO_(9) is related to the combined effects of magnetic frustration and criticality-enhanced MCE,which together leave substantial magnetic entropy at reduced temperatures by enhancing spin fluctuations.展开更多
Magnetic refrigeration(MR)technology is regarded as an ideal solution for cryogenic applications,relying on magnetocaloric materials which provide necessary chilling effect.A series of polycrystalline Tm_(1-x)Er_(x)Ni...Magnetic refrigeration(MR)technology is regarded as an ideal solution for cryogenic applications,relying on magnetocaloric materials which provide necessary chilling effect.A series of polycrystalline Tm_(1-x)Er_(x)Ni_(2)Si_(2)(x=0.2,0.4)compounds was synthesized,and their magnetic properties,magnetic phase transition together with magnetocaloric effect(MCE)were studied.The Tm_(1-x)Er_(x)Ni_(2)Si_(2)(x=0.2,0.4)compounds display a field-induced metamagnetic transition from antiferromagnetic(AFM)to ferromagnetism(FM)in excess of 0.2 T,respectively.Meanwhile,the AFM ground state is unstable.Under the field change of 0-2 T,the values of maximal magnetic entropy change(-ΔS_(M)^(max))and refrigerant capacity(RC)for Tm_(0.8)Er_(0.2)Ni_(2)Si_(2)compound are 17.9 J/(kg·K)and 83.5 J/kg,respectively.The large reversible MCE under low magnetic fields(≤2 T)indicates that Tm_(0.8)Er_(0.2)Ni_(2)Si_(2)compound can serve as potential candidate materials for cryogenic magnetic refrigeration.展开更多
With the rapid development of artificial intelligence,magnetocaloric materials as well as other materials are being developed with increased efficiency and enhanced performance.However,most studies do not take phase t...With the rapid development of artificial intelligence,magnetocaloric materials as well as other materials are being developed with increased efficiency and enhanced performance.However,most studies do not take phase transitions into account,and as a result,the predictions are usually not accurate enough.In this context,we have established an explicable relationship between alloy compositions and phase transition by feature imputation.A facile machine learning is proposed to screen candidate NiMn-based Heusler alloys with desired magnetic entropy change and magnetic transition temperature with a high accuracy R^(2)≈0.98.As expected,the measured properties of prepared NiMn-based alloys,including phase transition type,magnetic entropy changes and transition temperature,are all in good agreement with the ML predictions.As well as being the first to demonstrate an explicable relationship between alloy compositions,phase transitions and magnetocaloric properties,our proposed ML model is highly predictive and interpretable,which can provide a strong theoretical foundation for identifying high-performance magnetocaloric materials in the future.展开更多
High-entropy materials have attracted considerable attention in recent years owing to their unique structural characteristics,tailorable chemical composition,and tunable functional properties.In this study,the concept...High-entropy materials have attracted considerable attention in recent years owing to their unique structural characteristics,tailorable chemical composition,and tunable functional properties.In this study,the concept of entropy-mediated phase stabilization was combined with strongly correlated electron systems to achieve directional property control in single-phase manganites.As Ca and Cr are sequentially doped into(Pr_(0.25)La_(0.25)Nd_(0.25)Sm_(0.25))MnO_(3) at specific contents,the original weak ferromagnetic(FM)state with a spin-canted antiferromagnetic(AFM)background transforms into the charge-ordered AFM state,and then further transitions to the intense FM-AFM competition state.Magnetic state evolution also causes significant changes in electrical properties,highlighting the complex magnetoelectronic phase diagram of this system.Under specific doping conditions,the system exhibits a temperature-induced metamagnetic transition and a significant magnetocaloric effect,demonstrating interesting properties brought about by magnetic phase transitions.The complex magnetoelectric behavior induced by the coexistence and competition of multiple interactions is discussed by combining microstructural characterization with a magnetic theory framework.This study explores a method for effectively manipulating the physical properties of manganites based on the high-entropy concept,which is conducive to the development of new functional materials with kaleidoscopic characteristics.展开更多
The magnetic and magnetocaloric performances of the ternary Fe_(87)M_(10)B_(3)(M=Zr,Pr) amorphous alloys were systematically studied in the present work.By complete Pr substitution for Zr,the maximum magnetic entropy ...The magnetic and magnetocaloric performances of the ternary Fe_(87)M_(10)B_(3)(M=Zr,Pr) amorphous alloys were systematically studied in the present work.By complete Pr substitution for Zr,the maximum magnetic entropy change(-ΔS_(m)^(peak)) under 5 T is significantly enlarged from about 3.22 J/(kg·K) at 293 K to 4.66 J/(kg·K) at 337 K,with a simultaneous slight increase of magnetic hysteresis at 10 K.The mechanism involved was investigated with the help of first-principles simulation and magnetic force microscopy observation.The coercivity of the Fe_(87)Pr_(10)B_(3) amorphous ribbon at 10 K,which is induced by the strong random magnetic anisotropy that is related to the charge transfer from Pr atoms to Fe atoms,decreases to nearly zero at 200 K,indicating that the coercivity does not affect the magnetocaloric properties near room temperature.The enhanced Curie temperature(T_(c)) and the significantly enlarged-ΔS_(m)^(peak) are supposed to be closely related to a combination of the reinforced 3d-3d interaction and the introduction of 4f-4f interaction by complete Pr substitution for Zr.展开更多
The assembly of the three-dimensional(3D) lanthanide complexes,aiming at obtaining large magnetocalo ric effects,encounte rs a substantial challenge.In this study,we successfully isolated a novel series of Lnexclusive...The assembly of the three-dimensional(3D) lanthanide complexes,aiming at obtaining large magnetocalo ric effects,encounte rs a substantial challenge.In this study,we successfully isolated a novel series of Lnexclusive 3D complexes,fo rmulated as {[Ln_(2)(EDTA)(C_(2)O_(4))(H_(2)O)_(2)]}n(abbreviated as Ln_(2),Ln=Gd^(Ⅲ)(1),Eu^(Ⅲ)(2),Sm^(Ⅲ)(3),H_(4)EDTA=ethylene diamine tetraacetic acid;H_(2)C_(2)O_(4)=oxalic acid).Crystallographic study exhibits that complex 1 features a cute snail-shaped Gd_(2) unit.Adjacent Gd_(2) units are aggregated by hexadentate EDTA^(4-) and C_(2)O_(4)^(2-)ligands,further constructing a charming three-dimensional metal-organic framework with interesting parallelogram-shaped layers.Notably,all coordinated EDTA^(4-)ligands and lightweight C_(2)O_(4)^(2-)groups contribute to building a densely packed metal-organic framework,endowing complex 1 with remarkable magnetocaloric effect(-ΔS_(m)^(max)=42.5 J/(kg·K) at 2.5 K and ΔH=7.0 T).Additionally,complexes 2 and 3 exhibit outstanding solid-state luminescent properties with lifetimes of43 8.22 and 4.13 μs,and quantum yields(QY) of 7.03% and 15.46%,respectively.展开更多
Frustrated lanthanide oxides with dense magnetic lattice and suppressed ordering temperature have potential applications in cryogenic magnetic refrigeration.Herein,the crystal structure,magnetic properties,magnetic ph...Frustrated lanthanide oxides with dense magnetic lattice and suppressed ordering temperature have potential applications in cryogenic magnetic refrigeration.Herein,the crystal structure,magnetic properties,magnetic phase transition(MPT)together with magnetocaloric effect(MCE)of LnOF(Ln=Gd,Dy,Ho,and Er)compounds were investigated.Crystallographic study shows that these compounds crystallize in the centrosymmetric space group R3m with an ideal triangular lattice.No long-range magnetic ordering is observed above 2 K for LnOF(Ln=Gd,Ho,and Er).However,DyOF compound undergoes an MPT from paramagnetic(PM)to antiferromagnetic(AFM)at the Neel temperature(TN≈4 K).Considerable reversible MCE is observed in these triangular-lattice compounds.Under the magnetic field change(μ0ΔH)of 0-2 T,the maximum values of magnetic entropy change(-ΔSMmax)of them are 6.1,9.4,12.7,and 14.1 J/(kg·K),respectively.Interestingly,the value of ErOF with Ising-like spin is 2.3 times that of GdOF,which provides an approach for exploring magnetic refrigerants with excellent low-field cryogenic magnetocaloric effect.展开更多
Cryogenic magnetic cooling based on the principle of the magnetocaloric effects(MCEs)of magnetic solids has been recognized as an alternative cooling technology due to its significant economic and social benefits.Desi...Cryogenic magnetic cooling based on the principle of the magnetocaloric effects(MCEs)of magnetic solids has been recognized as an alternative cooling technology due to its significant economic and social benefits.Designing novel magnetic materials with good magnetocaloric performance is a prerequisite for practical applications.In this study,three gadolinium-transition metal-based high entropy oxides(HEOs)of Gd(Fe_(1/4)Ni_(1/4)Al_(1/4)Cr_(1/4))O_(3),Gd(Fe_(1/5)Ni_(1/5)Al_(1/5)Cr_(1/5)Co_(1/5))O_(3),and Gd(Fe_(1/6)Ni_(1/6)Al_(1/6)Cr_(1/6)Co_(1/6)Mn_(1/6))O_(3)were designed and systematically characterized regarding their structural and cryogenic magnetic properties.These HEOs were confirmed to crystallize into a single-phase perovskite-type orthorhombic structure with a homogeneous microstructure,reveal a second-order magnetic transition at low temperatures,and exhibit significant cryogenic MCEs.The magnetocaloric performances of the present HEOs,identified by magnetic entropy changes,relative cooling power,and temperature-averaged entropy changes,were com-parable with recently reported candidate materials.The present study indicates potential applications for cryogenic magnetic cooling of the present HEOs and provides meaningful clues for designing and exploring HEOs with good cryogenic magnetocaloric performances.展开更多
This study investigated the effects of interstitial carbon doping on the microstructural and magnetocaloric properties of off-stoichiometric La_(1.2)Fe_(11.6)Si_(1.4)Cx(x=0,0.25,0.5,0.75,1)alloys.The alloys were prepa...This study investigated the effects of interstitial carbon doping on the microstructural and magnetocaloric properties of off-stoichiometric La_(1.2)Fe_(11.6)Si_(1.4)Cx(x=0,0.25,0.5,0.75,1)alloys.The alloys were prepared by melt-spinning following vacuum arc-melting.For the as-prepared and annealed samples,the carbon existed in the La_(2)Fe_(2)Si_(2)C and NaZn_(13)-type La(Fe,Si)_(13)(denoted by 1:13)phases,respectively.During the annealing process,the C atoms inhibited the diffusion reaction and depressed the generation of 1:13 phase,reducing mass fraction of the 1:13 phase in annealed La_(1.2)Fe_(11.6)Si_(1.4)Cx compounds.The introduction of carbon resulted in lattice expansion and increased the Curie temperature(T_(C))from 192 K to 273 K with x=0.5.The first-order magnetic transition was gradually transformed into the second-order magnetic transition with increasing carbon content,which induced the significant reduction of thermal and magnetic hysteresis,as well as the maximum magnetic entropy change and adiabatic temperature change vary from 18.92 J/(kg·K)to 4.60 J/(kg·K)and from 4.9 K to 2.2 K under an applied field change of 0-2 T.The results demonstrate that interstitial carbon doping is an effective strategy to improve the magnetocaloric performance of La(Fe,Si)_(13)alloys.展开更多
The rare earth(RE)-transition metal(TM)based compounds have emerged as one of the best candi-dates for the application in eco-friendly and effective cooling technology due to their outstanding cryogenic magnetocaloric...The rare earth(RE)-transition metal(TM)based compounds have emerged as one of the best candi-dates for the application in eco-friendly and effective cooling technology due to their outstanding cryogenic magnetocaloric performances.In this work,three RE-TM germanides RE_(3)Co_(2)Ge_(4)(RE=Gd,Tb and Dy)were synthesized and characterized,aiming to investigating their structural,magnetic and magnetocaloric properties.These compounds crystallize in the Tb_(3)Co_(2)Ge_(4)-type monoclinic structure(space group C2/m,Z=2).Two successive ferromagnetic transitions are observed with T_(c) of 31 and 135 K for Gd_(3)Co_(2)Ge_(4),ferromagnetic and spin reorientation transitions are observed with Tc of 24 K and T_(s) of 19 K for Dy_(3)Co_(2)Ge_(4),all of which are second ordered.In contrast,Tb_(3)Co_(2)Ge_(4)exhibits a second order antiferromagnetic transition with T_(n) of 36 K,accompanied with a spin reorientation transition with T_(s) of 17 K.Furthermore,the ferromagnetic ground state for Gd_(3)Co_(2)Ge_(4)is also confirmed by the first-principles calculations.Significant cryogenic magnetocaloric performances are observed in these compounds,.The determined maximum magnetic entropy change(-ΔS_(M)^(max))under a magnetic field change(△H)of 0-7 T are 10.7,5.3 and 11.6 J/(kg·K)for Gd_(3)Co_(2)Ge_(4),Tb_(3)Co_(2)Ge_(4)and Dy_(3)Co_(2)Ge_(4),respectively.Our results suggest that Gd_(3)Co_(2)Ge_(4)and Dy_(3)Co_(2)Ge_(4)compounds are attractive candidates for cryogenic magnetic refrigeration applications.展开更多
The magnetic refrigeration(MR)based on the principle of magnetocaloric effect(MCE)in magnetic materials was recognized as an alternative cooling way to our present commercialized vapor compression cycle technology.Evi...The magnetic refrigeration(MR)based on the principle of magnetocaloric effect(MCE)in magnetic materials was recognized as an alternative cooling way to our present commercialized vapor compression cycle technology.Evidently,a vital prerequisite for practical applications is the exploration of candidate materials with prominent magnetocaloric performances.In this paper,the polycrystalline garnet RE_(3)Al_(5)O_(12)(RE=Tb,Dy and Ho)compounds with the cubic structure(space group:Ia3d)were prepared using the Pechini sol-gel method,and their crystal structure,magnetic properties and comprehensive magnetocaloric performances were studied.The analysis of magnetic susceptibility curves in a static magnetic field H=0.1 T reveal that the Dy_(3)Al_(5)O_(12)undergoes antiferromagnetic transition with Néel temperature TN≈2.6 K,whereas the Tb_(3)Al_(5)O_(12)and Ho_(3)Al_(5)O_(12)exhibit no features indicative of the magnetic ordering processes down to 1.8 K.The comprehensive magnetocaloric performances,namely the maximum magnetic entropy change and relative cooling power,are derived indirectly from the isothermal field-dependent magnetization data,which yield 11.72,10.42,7.53 J/(kg·K)and 84.56,69.52,70.35 J/kg for the Tb_(3)Al_(5)O_(12),Dy_(3)Al_(5)O_(12)and Ho_(3)Al_(5)O_(12)under a low field change(ΔH)of 0-2 T,respectively.The superior comprehensive magnetocaloric performances and wide operating temperature range of these compounds under lowΔH make them attractive for cryogenic MR technology.展开更多
Magnetocaloric material is the key working substance for magnetic refrigerant technology,for which the low-field and low-temperature magnetocaloric effect(MCE)performance is of great importance for practical applicati...Magnetocaloric material is the key working substance for magnetic refrigerant technology,for which the low-field and low-temperature magnetocaloric effect(MCE)performance is of great importance for practical applications at low temperatures.Here,a giant low-field magnetocaloric effect in ferromagnetically ordered Er_(1-x)Tm_(x)Al_(2)(0≤x≤1)compounds was reported,and the magnetic structure was characterized based on low-temperature neutron powder diffraction.With increasing Tm content from 0 to 1,the Curie temperature of Er_(1-x)Tm_(x)Al_(2)(0≤x≤1)compounds decreases from 16.0 K to 3.6 K.For Er_(0.7)Tm_(0.3)Al_(2) compound,it showed the largest low-field magnetic entropy change(–SM)with the peak value of 17.2 and 25.7 J/(kg K)for 0–1 T and 0–2 T,respectively.The(–SM)max up to 17.2 J/(kg K)of Er0.7Tm0.3Al2 compound for 0–1 T is the largest among the intermetallic magnetocaloric materials ever reported at temperatures below 20 K.The peak value of adiabatic temperature change(Tad)max was determined as 4.13 K and 6.87 K for 0–1 T and 0–2 T,respectively.The characteristic of second-order magnetic transitions was confirmed on basis of Arrott plots,the quantitative criterion of exponent n,rescaled universal curves,and the mean-field theory criterion.The outstanding low-field MCE performance with low working temperatures indicates that Er_(1-x)Tm_(x)Al_(2)(0≤x≤1)compounds are promising candidates for magnetic cooling materials at liquid hydrogen and liquid helium temperatures.展开更多
Magnetic refrigeration based on the magnetocaloric effect(MCE)of magnetic solids has been considered as an emerging technology for hydrogen liquefaction.However,the lack of high-performance materials has slowed the de...Magnetic refrigeration based on the magnetocaloric effect(MCE)of magnetic solids has been considered as an emerging technology for hydrogen liquefaction.However,the lack of high-performance materials has slowed the development of any practical applications.Here,we present a family of rare-earth cobalt nickel-based magnetocaloric materials,namely Dy_(1-x)Ho_(x)CoNi and Ho_(1-x)Er_(x)CoNi compounds,and system-atically investigated their structural and magnetic properties as well as the MCE and magnetocaloric per-formance.All of these compounds crystallize in the C15-type Laves-phase structure and undergo typi-cal second-order magnetic phase transition(MPT).The change in magnetism and the MPT temperature for the Dy_(1-x)Ho_(x)CoNi and Ho_(1-x)Er_(x)CoNi compounds originate from the exchange interactions between nearest-neighbor RE 3+ion pairs.No hysteresis magnetocaloric effect was achieved,and the MPT tem-perature of these compounds could be tuned from the liquefaction temperature of nitrogen(∼77 K)to hydrogen(∼20 K)by adjusting the ratio of rare-earth elements.This study’s findings indicate that theDy_(1-x)Ho_(x)CoNi and Ho_(1-x)Er_(x)CoNi compounds are of potential for practical magnetic refrigeration applica-tions in the field of hydrogen liquefaction.展开更多
The magnetocaloric effect（MCE） of RT Si and RT Al systems with R = Gd–Tm, T = Fe–Cu and Pd, which have been widely investigated in recent years, is reviewed. It is found that these RT X compounds exhibit various c...The magnetocaloric effect（MCE） of RT Si and RT Al systems with R = Gd–Tm, T = Fe–Cu and Pd, which have been widely investigated in recent years, is reviewed. It is found that these RT X compounds exhibit various crystal structures and magnetic properties, which then result in different MCE. Large MCE has been observed not only in the typical ferromagnetic materials but also in the antiferromagnetic materials. The magnetic properties have been studied in detail to discuss the physical mechanism of large MCE in RT X compounds. Particularly, some RT X compounds such as Er Fe Si,Ho Cu Si, Ho Cu Al exhibit large reversible MCE under low magnetic field change, which suggests that these compounds could be promising materials for magnetic refrigeration in a low temperature range.展开更多
The investigation on Curie temperature and magnetocaloric effect of the FeCrMoCBYNi bulk metallic glass(BMG) with different crystallized phases was carried out by XRD,TEM and PPMS. The experimental results show that t...The investigation on Curie temperature and magnetocaloric effect of the FeCrMoCBYNi bulk metallic glass(BMG) with different crystallized phases was carried out by XRD,TEM and PPMS. The experimental results show that the Curie temperature(T_c) of Fe_(45)Cr_(15)Mo_(14)C_(15)B_6 Y_2 Ni_3 BMG with different annealing condition reaches a highest value of 95 K. The value of magnetic entropy change △S_M(T) of Sample 3 reaches a maxima of 0.48 J/(kg·K) at Tc temperature, which result from the interaction among the precipitated phases of(Fe,Cr)_(23)(C,B)_6, Fe_3 Mo_3 C and residual amorphous phase. Based on the experiment results, it can be obtained that the Curie temperature, magnetocaloric effect can reach their optimal value at low temperature, when the content of amorphous phase and precipitated phases type run up to certain value. The magnetic properties of Sample 1 with full amorphous phase and Sample 4 with full crystalline phase will both decrease.展开更多
The research on magnetocaloric materials for applications concentrates,among other,on two parameters:the ordering temperature and the value of the magnetocaloric effect(MCE).The optimization consists in tuning the for...The research on magnetocaloric materials for applications concentrates,among other,on two parameters:the ordering temperature and the value of the magnetocaloric effect(MCE).The optimization consists in tuning the former without significant drop in the latter.These studies report on the magnetic susceptibility,magnetization curves,heat capacity and magnetocaloric effect measurements for compositionally and structurally modified Gd5Si4 compound.The modifications are based on the doping of the parent compound with an excess Gd atoms and substitution of Si with B as well as on the dimensional effect studied by mechanical milling.Moreover,composite samples of the type Gd:Gd5Si2Ge2 were investigated revealing the influence of the intergranular interactions on the magnetocaloric properties.It appears that these interventions enable a controllable steering of the ordering temperature shifting it towards the room temperature with,in some cases,minor reduction of the parameters characterizing MCE.展开更多
Three binuclear rare earth based complexes combining RE ions with semirigid tricarboxylic ligand(H_(3)L).namely,[RE_(2)(L)_(2)(DMF)_(4)][RE=Gd,Tb,and Dy;H_(3)L=5-((4-Carboxybenzyl)oxy)isophthalic acid;DMF=N,N-dimethyl...Three binuclear rare earth based complexes combining RE ions with semirigid tricarboxylic ligand(H_(3)L).namely,[RE_(2)(L)_(2)(DMF)_(4)][RE=Gd,Tb,and Dy;H_(3)L=5-((4-Carboxybenzyl)oxy)isophthalic acid;DMF=N,N-dimethylformamide]complexes,were fabricated success fully.The RE_(2)(L)_(2)(DMF)_(4) co mplexe s consist of two central RE ions with the same coordination environment which were connected by two tridentate bridging carboxylic groups and two syn-syn bidentate bridging carboxylic groups originating from the L^(3-)ligands to form the{RE_(2)}dimeric unit,and thus provides the basis for further constructing a dense three-dimensional(3 D)network structure.Moreover,the present RE_(2)(L)_(2)(DMF)_(4) complexes can be described by a topology diagram with the topology point symbol of{4^(2)·6}_(2){4^(4)·6^(2)·8^(7)·10^(2)}.Weak antiferromagnetic(AFM)coupling between the adjacent RE ions for all the present complexes was found according to the magnetic calculations.The observed significant cryogenic magnetocaloric effect(MCE)with the maximum magnetic entropy change-ΔS_(M)^(max) to be 26.3 J/(kg·K)withΔH=7 T in Gd_(2)(L)_(2)(DMF)_(4) complex makes it competitive for the cryogenic magnetic refrigerant.Moreover,the slow magnetic relaxation behavior at 0.2 T dc field with an obvious large U_(eff)/k=45(4)K and τ_(0)=6.5(2)×10^(-10)s was confirmed in Dy_(2)(L)_(2)(DMF)_(4)complex.This work not only provides an effective strategy for obtaining molecular materials with high MCE,but also confirms that tricarboxylate ligands are the ideal choice for constructing stable high dimensional geometric structures.展开更多
基金Project supported by the National Key Research and Decelopment Program of China(Grant No.2021YFB3500302)the National Natural Science Foundation of China(Grant Nos.U22A20116 and 52371200)the Innovation Capability Improvement Project of Hebei Province,China(Grant No.22567605H)。
文摘Large magnetic entropy change(△S_(M))can realize a prominent heat transformation under the magnetic field and directly strengthen the efficacy of the magnetocaloric effect,which provides a pioneering environmentally friendly solidstate strategy to improve refrigeration capacities and efficiencies.The second-order magnetic transition(SOMT)materials have broader△S_(M) peaks without thermal hysteresis,making them highly attractive in magnetic refrigeration,especially in the room temperature range.Here,we report a significant enhancement of△S_(M) at room temperature in single-crystal Mn_(5)Ge_(3).In this SOMT system,we realize a 60%improvement of-△S_(M)^(max) from 3.5 J/kg·K to 5.6 J/kg·K at T=300 K.This considerable enhancement of△S_(M) is achieved by intentionally introducing strain energy through high-pressure constrained deformation.Both experimental results and Monte Carlo simulations demonstrate that the enhancement of△S_(M) originates from the microscopic strain and lattice deformation induced by strain energy after deformation.This strain energy will reconstruct the energy landscape of this ferromagnetic system and enhance magnetization,resulting in a giant intensity of magnetocaloric responses.Our findings provide an approach to increase magnetic entropy change and may give fresh ideas for exploring advanced magnetocaloric materials.
基金funded by the European Union within CoCoMag Project(Grant No.101099736)Project PID2023-146047OB-I00(from AEI/10.13039/501100011033)+3 种基金Project PPIT2024-31833,co-financed by EU,Ministerio de Hacienda y Función Publica,FEDER and Junta de Andalucía,and VII Plan Propio de Investigación from University of SevilleE.G.A.acknowledges an FPU scholarship(Ref.FPU23/03426)from the Spanish MICIUC.R.M.acknowledges financial support by the Ramón y Cajal program of the Spanish Ministry of Science and Innovation(Ref.RYC2021-031176-I)J.Y.L.acknowledges an EMERGIA 2021 fellowship from Junta de Andalucía(Ref.EMC21_00418).
文摘Rising global temperatures alongside increasing energy demand highlight the imperative for sustainable and energy-efficient refrigeration technologies.Magnetic refrigeration,based on the magnetocaloric effect(MCE),presents a compelling solid-state alternative to traditional vapor-compression systems.However,many high-performance magnetocaloric materials rely on critical elements such as rare earths,cobalt and germanium.Despite extensive compositional flexibility,high-entropy alloys(HEAs)have predominantly been investigated in equiatomic compositions incorporating significant quantities of highly critical elements to achieve large MCE or mixing rare-earth elements in majority proportions that only yield moderate MCE values,thereby failing to address issues of material criticality.In this study,we present a criticality-aware design strategy for the MnNiSi-HEA system,exemplifying a prototype of the latest third-generation HEAs.Various substitutional approaches were evaluated to achieve the coupling between magnetic and structural transitions.The most effective pathway,identified through the co-substitution of Fe and Cu reduces the structural transition temperature by over 900 K relative to MnNiSi while preserving the ferromagnetic characteristics of the low-temperature phase,successfully inducing a first-order magnetostructural transformation near room temperature.The resulting alloys,Mn_(0.5)Fe_(0.5)Ni_(1−x)Cu_(x)Si,exhibit coupled transitions spanning more than 100 K and demonstrate the highest MCE reported to date among HEAs free of cobalt,germanium and rare-earth elements,outperforming previous records by 360%.Complementary density functional theory calculations confirm the stability of the orthorhombic and hexagonal phases.Predictions of lattice entropy change closely match calorimetric measurements.This study establishes a new benchmark for low-criticality magnetocaloric HEAs,underscoring that optimal functional performance and sustainable material development can be achieved concomitantly.The proposed design methodology offers a valuable framework for advancing resource-resilient solid-state cooling materials and underscores the potential of HEAs as a platform for sustainable functional materials.
基金financially supported by the National Sci-ence Foundation for Young Scientists of China(Nos.52201172,52201171,52401219)the National Science Fund for Distinguished Young Scholars(No.52225103)+4 种基金the National Natural Science Foundation of China(No.52130108)the National Key R&D Program of China(No.2022YFB4602101)the Joint Funds of the National Natural Science Foundation of China(No.U2441262)the Funds for International Cooperation and Exchange of the National Nat-ural Science Foundation of China(No.W2412068)the Fundamental Research Fund for the Central Universities of China(No.FRF-TP-22-001C2).
文摘High-entropy magnetocaloric alloys offer exceptional compositional flexibility and stability for magnetic refrigeration.However,enhancing their magnetic entropy change,working temperature range,and refrigeration capacity remains challenging.In this study,we demonstrate that microalloying GdTbDyHo with only 0.4at%nonmagnetic Y effectively addresses this limitation.Our analysis indicates that Y uniformly dissolves into the hexagonal matrix lattice,disrupting the 4f–4f exchange interactions and inducing a local short-range order.This weakens the antiferromagnetic coupling,accelerates the antiferromagnetic–ferromagnetic transition,and broadensits range.Consequently,the peak magnetic entropy change increases from 8.2 to 8.7 J·kg^(−1)·K^(−1),the working temperature range expands from 77 to 89 K,and the refrigeration capacity improves by 23%,reaching 774 J·kg^(−1)(5 T)relative to the Y-free alloy,while the Néel temperature remains constant(~195 K).This study establishes nonmagnetic microalloying as a cost-effective and scalable strategy for designing high-performance magnetocaloric materials.
基金supported by the National Key Research and Development Program(Grant Nos.2024YFA1611200 and 2023YFA1406500)the National Natural Science Foundation of China(Grant Nos.12141002 and 52088101)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB1270000)。
文摘Rare-earth based frustrated magnets have attracted great attention as excellent candidates for magnetic refrigeration at sub-Kelvin temperatures,while the experimental identification of systems exhibiting both large volumetric cooling capacity and reduced working temperatures far below 1K remains a challenge.Here,through ultra-low temperature magnetism and thermodynamic characterizations,we unveil the large magnetocaloric effect(MCE)realized at sub-Kelvin temperatures in the frustrated Kagome antiferromagnet Gd_(3)BWO_(9) with T_(N)∼1.0 K.The isothermal magnetization curves indicate the existence of field(B)induced anisotropic magnetic phase diagrams,where four distinct magnetic phases for B‖c-axis and five magnetic phases for B‖ab-plane are identified at T<T_(N).The analysis of magnetic entropy S(B,T)data and direct adiabatic demagnetization tests reveal remarkable cooling performance at sub-Kelvin temperatures featured by a large volumetric entropy density of 502.2 mJ/K/cm^(3)and a low attainable minimal temperature T_(min)∼168mK from the initial cooling condition of 2K and 6 T,surpassing most Gd-based refrigerants previously documented in temperature ranges of 0.25–4 K.The realized T_(min)∼168mK far below T_(N)∼1.0K in Gd_(3)BWO_(9) is related to the combined effects of magnetic frustration and criticality-enhanced MCE,which together leave substantial magnetic entropy at reduced temperatures by enhancing spin fluctuations.
基金Project supported by the National Key Research and Development Program of China(2021YFB3501204)the National Natural Science Foundation of China(52171054)+1 种基金the National Science Foundation for Distinguished Young Scholars(51925605)the National Science Foundation for Excellent Young Scholars(52222107)。
文摘Magnetic refrigeration(MR)technology is regarded as an ideal solution for cryogenic applications,relying on magnetocaloric materials which provide necessary chilling effect.A series of polycrystalline Tm_(1-x)Er_(x)Ni_(2)Si_(2)(x=0.2,0.4)compounds was synthesized,and their magnetic properties,magnetic phase transition together with magnetocaloric effect(MCE)were studied.The Tm_(1-x)Er_(x)Ni_(2)Si_(2)(x=0.2,0.4)compounds display a field-induced metamagnetic transition from antiferromagnetic(AFM)to ferromagnetism(FM)in excess of 0.2 T,respectively.Meanwhile,the AFM ground state is unstable.Under the field change of 0-2 T,the values of maximal magnetic entropy change(-ΔS_(M)^(max))and refrigerant capacity(RC)for Tm_(0.8)Er_(0.2)Ni_(2)Si_(2)compound are 17.9 J/(kg·K)and 83.5 J/kg,respectively.The large reversible MCE under low magnetic fields(≤2 T)indicates that Tm_(0.8)Er_(0.2)Ni_(2)Si_(2)compound can serve as potential candidate materials for cryogenic magnetic refrigeration.
基金supported by the National Key R&D Program of China(No.2022YFE0109500)the National Natural Science Foundation of China(Nos.52071255,52301250,52171190 and 12304027)+2 种基金the Key R&D Project of Shaanxi Province(No.2022GXLH-01-07)the Fundamental Research Funds for the Central Universities(China)the World-Class Universities(Disciplines)and the Characteristic Development Guidance Funds for the Central Universities.
文摘With the rapid development of artificial intelligence,magnetocaloric materials as well as other materials are being developed with increased efficiency and enhanced performance.However,most studies do not take phase transitions into account,and as a result,the predictions are usually not accurate enough.In this context,we have established an explicable relationship between alloy compositions and phase transition by feature imputation.A facile machine learning is proposed to screen candidate NiMn-based Heusler alloys with desired magnetic entropy change and magnetic transition temperature with a high accuracy R^(2)≈0.98.As expected,the measured properties of prepared NiMn-based alloys,including phase transition type,magnetic entropy changes and transition temperature,are all in good agreement with the ML predictions.As well as being the first to demonstrate an explicable relationship between alloy compositions,phase transitions and magnetocaloric properties,our proposed ML model is highly predictive and interpretable,which can provide a strong theoretical foundation for identifying high-performance magnetocaloric materials in the future.
基金supported by the National Natural Science Foundation of China(Nos.12074204,12374258 and 12404326)the Natural Science Foundation of Inner Mongolia Autonomous Region of China(Nos.2022ZD06 and 2023QN01008)+3 种基金the Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(No.NMGIRT2203)the Research Program of Science and Technology at Universities of Inner Mongolia Autonomous Region(No.NJZZ23024)the Fundamental Research Funds for the Inner Mongolia Normal University(No.2023JBYJ015)the Funds for Reform and Development of Local Universities Supported by the Central Government(Cultivation of First-Class Disciplines in Physics).
文摘High-entropy materials have attracted considerable attention in recent years owing to their unique structural characteristics,tailorable chemical composition,and tunable functional properties.In this study,the concept of entropy-mediated phase stabilization was combined with strongly correlated electron systems to achieve directional property control in single-phase manganites.As Ca and Cr are sequentially doped into(Pr_(0.25)La_(0.25)Nd_(0.25)Sm_(0.25))MnO_(3) at specific contents,the original weak ferromagnetic(FM)state with a spin-canted antiferromagnetic(AFM)background transforms into the charge-ordered AFM state,and then further transitions to the intense FM-AFM competition state.Magnetic state evolution also causes significant changes in electrical properties,highlighting the complex magnetoelectronic phase diagram of this system.Under specific doping conditions,the system exhibits a temperature-induced metamagnetic transition and a significant magnetocaloric effect,demonstrating interesting properties brought about by magnetic phase transitions.The complex magnetoelectric behavior induced by the coexistence and competition of multiple interactions is discussed by combining microstructural characterization with a magnetic theory framework.This study explores a method for effectively manipulating the physical properties of manganites based on the high-entropy concept,which is conducive to the development of new functional materials with kaleidoscopic characteristics.
基金Project supported by the National Natural Science Foundation of China (51871139, 52071196, 52071043)。
文摘The magnetic and magnetocaloric performances of the ternary Fe_(87)M_(10)B_(3)(M=Zr,Pr) amorphous alloys were systematically studied in the present work.By complete Pr substitution for Zr,the maximum magnetic entropy change(-ΔS_(m)^(peak)) under 5 T is significantly enlarged from about 3.22 J/(kg·K) at 293 K to 4.66 J/(kg·K) at 337 K,with a simultaneous slight increase of magnetic hysteresis at 10 K.The mechanism involved was investigated with the help of first-principles simulation and magnetic force microscopy observation.The coercivity of the Fe_(87)Pr_(10)B_(3) amorphous ribbon at 10 K,which is induced by the strong random magnetic anisotropy that is related to the charge transfer from Pr atoms to Fe atoms,decreases to nearly zero at 200 K,indicating that the coercivity does not affect the magnetocaloric properties near room temperature.The enhanced Curie temperature(T_(c)) and the significantly enlarged-ΔS_(m)^(peak) are supposed to be closely related to a combination of the reinforced 3d-3d interaction and the introduction of 4f-4f interaction by complete Pr substitution for Zr.
基金Project supported by the National Natural Science Foundation of China (92161109)the Postgraduate Research&Practice Innovation Program of Jiangsu Province (KYCX24_1566)。
文摘The assembly of the three-dimensional(3D) lanthanide complexes,aiming at obtaining large magnetocalo ric effects,encounte rs a substantial challenge.In this study,we successfully isolated a novel series of Lnexclusive 3D complexes,fo rmulated as {[Ln_(2)(EDTA)(C_(2)O_(4))(H_(2)O)_(2)]}n(abbreviated as Ln_(2),Ln=Gd^(Ⅲ)(1),Eu^(Ⅲ)(2),Sm^(Ⅲ)(3),H_(4)EDTA=ethylene diamine tetraacetic acid;H_(2)C_(2)O_(4)=oxalic acid).Crystallographic study exhibits that complex 1 features a cute snail-shaped Gd_(2) unit.Adjacent Gd_(2) units are aggregated by hexadentate EDTA^(4-) and C_(2)O_(4)^(2-)ligands,further constructing a charming three-dimensional metal-organic framework with interesting parallelogram-shaped layers.Notably,all coordinated EDTA^(4-)ligands and lightweight C_(2)O_(4)^(2-)groups contribute to building a densely packed metal-organic framework,endowing complex 1 with remarkable magnetocaloric effect(-ΔS_(m)^(max)=42.5 J/(kg·K) at 2.5 K and ΔH=7.0 T).Additionally,complexes 2 and 3 exhibit outstanding solid-state luminescent properties with lifetimes of43 8.22 and 4.13 μs,and quantum yields(QY) of 7.03% and 15.46%,respectively.
基金Project supported by the National Key Research and Development Program of China(2022YFB3505101)the National Science Foundation for Excellent Young Scholars(52222107)+2 种基金the National Science Foundation for Distinguished Young Scholars(51925605)the National Natural Science Foundation of China(52171195)the Projects of Ganjiang Innovation Academy,Chinese Academy of Sciences(E055B002)。
文摘Frustrated lanthanide oxides with dense magnetic lattice and suppressed ordering temperature have potential applications in cryogenic magnetic refrigeration.Herein,the crystal structure,magnetic properties,magnetic phase transition(MPT)together with magnetocaloric effect(MCE)of LnOF(Ln=Gd,Dy,Ho,and Er)compounds were investigated.Crystallographic study shows that these compounds crystallize in the centrosymmetric space group R3m with an ideal triangular lattice.No long-range magnetic ordering is observed above 2 K for LnOF(Ln=Gd,Ho,and Er).However,DyOF compound undergoes an MPT from paramagnetic(PM)to antiferromagnetic(AFM)at the Neel temperature(TN≈4 K).Considerable reversible MCE is observed in these triangular-lattice compounds.Under the magnetic field change(μ0ΔH)of 0-2 T,the maximum values of magnetic entropy change(-ΔSMmax)of them are 6.1,9.4,12.7,and 14.1 J/(kg·K),respectively.Interestingly,the value of ErOF with Ising-like spin is 2.3 times that of GdOF,which provides an approach for exploring magnetic refrigerants with excellent low-field cryogenic magnetocaloric effect.
基金supported by the National Natural Science Foundation of China(No.52171174).The authors acknowledge Dr.Chao Zhang from the Instrumentation Service Center for Physical Sciences at Westlake University for magnetization measurements.
文摘Cryogenic magnetic cooling based on the principle of the magnetocaloric effects(MCEs)of magnetic solids has been recognized as an alternative cooling technology due to its significant economic and social benefits.Designing novel magnetic materials with good magnetocaloric performance is a prerequisite for practical applications.In this study,three gadolinium-transition metal-based high entropy oxides(HEOs)of Gd(Fe_(1/4)Ni_(1/4)Al_(1/4)Cr_(1/4))O_(3),Gd(Fe_(1/5)Ni_(1/5)Al_(1/5)Cr_(1/5)Co_(1/5))O_(3),and Gd(Fe_(1/6)Ni_(1/6)Al_(1/6)Cr_(1/6)Co_(1/6)Mn_(1/6))O_(3)were designed and systematically characterized regarding their structural and cryogenic magnetic properties.These HEOs were confirmed to crystallize into a single-phase perovskite-type orthorhombic structure with a homogeneous microstructure,reveal a second-order magnetic transition at low temperatures,and exhibit significant cryogenic MCEs.The magnetocaloric performances of the present HEOs,identified by magnetic entropy changes,relative cooling power,and temperature-averaged entropy changes,were com-parable with recently reported candidate materials.The present study indicates potential applications for cryogenic magnetic cooling of the present HEOs and provides meaningful clues for designing and exploring HEOs with good cryogenic magnetocaloric performances.
基金supported by the National Natural Science Foundation of China(Grant No.52272263)the University Synergy Innovation Program of Anhui Province,China(Grant No.GXXT-2022-008)+2 种基金the University Natural Science Research Project of Anhui Province,China(Grant No.2024AH050145)the Youth Foundation of Anhui University of Technology(Grant No.QZ202303)the National Innovation and Entrepreneurship Training Program for College Students(Grant No.202310360018).
文摘This study investigated the effects of interstitial carbon doping on the microstructural and magnetocaloric properties of off-stoichiometric La_(1.2)Fe_(11.6)Si_(1.4)Cx(x=0,0.25,0.5,0.75,1)alloys.The alloys were prepared by melt-spinning following vacuum arc-melting.For the as-prepared and annealed samples,the carbon existed in the La_(2)Fe_(2)Si_(2)C and NaZn_(13)-type La(Fe,Si)_(13)(denoted by 1:13)phases,respectively.During the annealing process,the C atoms inhibited the diffusion reaction and depressed the generation of 1:13 phase,reducing mass fraction of the 1:13 phase in annealed La_(1.2)Fe_(11.6)Si_(1.4)Cx compounds.The introduction of carbon resulted in lattice expansion and increased the Curie temperature(T_(C))from 192 K to 273 K with x=0.5.The first-order magnetic transition was gradually transformed into the second-order magnetic transition with increasing carbon content,which induced the significant reduction of thermal and magnetic hysteresis,as well as the maximum magnetic entropy change and adiabatic temperature change vary from 18.92 J/(kg·K)to 4.60 J/(kg·K)and from 4.9 K to 2.2 K under an applied field change of 0-2 T.The results demonstrate that interstitial carbon doping is an effective strategy to improve the magnetocaloric performance of La(Fe,Si)_(13)alloys.
基金the Science and Technology Development Fund,Macao SAR,China(006/2022/ALC).
文摘The rare earth(RE)-transition metal(TM)based compounds have emerged as one of the best candi-dates for the application in eco-friendly and effective cooling technology due to their outstanding cryogenic magnetocaloric performances.In this work,three RE-TM germanides RE_(3)Co_(2)Ge_(4)(RE=Gd,Tb and Dy)were synthesized and characterized,aiming to investigating their structural,magnetic and magnetocaloric properties.These compounds crystallize in the Tb_(3)Co_(2)Ge_(4)-type monoclinic structure(space group C2/m,Z=2).Two successive ferromagnetic transitions are observed with T_(c) of 31 and 135 K for Gd_(3)Co_(2)Ge_(4),ferromagnetic and spin reorientation transitions are observed with Tc of 24 K and T_(s) of 19 K for Dy_(3)Co_(2)Ge_(4),all of which are second ordered.In contrast,Tb_(3)Co_(2)Ge_(4)exhibits a second order antiferromagnetic transition with T_(n) of 36 K,accompanied with a spin reorientation transition with T_(s) of 17 K.Furthermore,the ferromagnetic ground state for Gd_(3)Co_(2)Ge_(4)is also confirmed by the first-principles calculations.Significant cryogenic magnetocaloric performances are observed in these compounds,.The determined maximum magnetic entropy change(-ΔS_(M)^(max))under a magnetic field change(△H)of 0-7 T are 10.7,5.3 and 11.6 J/(kg·K)for Gd_(3)Co_(2)Ge_(4),Tb_(3)Co_(2)Ge_(4)and Dy_(3)Co_(2)Ge_(4),respectively.Our results suggest that Gd_(3)Co_(2)Ge_(4)and Dy_(3)Co_(2)Ge_(4)compounds are attractive candidates for cryogenic magnetic refrigeration applications.
基金supported by the National Natural Science Foundation of China(52301240,52472274)the Fundamental Research Funds for the Provincial Universities of Zhejiang(GK259909299001-022)。
文摘The magnetic refrigeration(MR)based on the principle of magnetocaloric effect(MCE)in magnetic materials was recognized as an alternative cooling way to our present commercialized vapor compression cycle technology.Evidently,a vital prerequisite for practical applications is the exploration of candidate materials with prominent magnetocaloric performances.In this paper,the polycrystalline garnet RE_(3)Al_(5)O_(12)(RE=Tb,Dy and Ho)compounds with the cubic structure(space group:Ia3d)were prepared using the Pechini sol-gel method,and their crystal structure,magnetic properties and comprehensive magnetocaloric performances were studied.The analysis of magnetic susceptibility curves in a static magnetic field H=0.1 T reveal that the Dy_(3)Al_(5)O_(12)undergoes antiferromagnetic transition with Néel temperature TN≈2.6 K,whereas the Tb_(3)Al_(5)O_(12)and Ho_(3)Al_(5)O_(12)exhibit no features indicative of the magnetic ordering processes down to 1.8 K.The comprehensive magnetocaloric performances,namely the maximum magnetic entropy change and relative cooling power,are derived indirectly from the isothermal field-dependent magnetization data,which yield 11.72,10.42,7.53 J/(kg·K)and 84.56,69.52,70.35 J/kg for the Tb_(3)Al_(5)O_(12),Dy_(3)Al_(5)O_(12)and Ho_(3)Al_(5)O_(12)under a low field change(ΔH)of 0-2 T,respectively.The superior comprehensive magnetocaloric performances and wide operating temperature range of these compounds under lowΔH make them attractive for cryogenic MR technology.
基金supported by the National Key Research and Development Program of China(Nos.2021YFB3501202 and 2019YFB2005800)the Science Center of the National Science Foundation of China(No.52088101)+1 种基金the National Natural Science Foundation of China(Nos.51871019,52171170,52130103,51961145305,51971026,and 52171169)the Beijing Natural Science Foundation Key Program(Grant Nos.Z190007 and Z200007),and“111 Project”(No.B170003).
文摘Magnetocaloric material is the key working substance for magnetic refrigerant technology,for which the low-field and low-temperature magnetocaloric effect(MCE)performance is of great importance for practical applications at low temperatures.Here,a giant low-field magnetocaloric effect in ferromagnetically ordered Er_(1-x)Tm_(x)Al_(2)(0≤x≤1)compounds was reported,and the magnetic structure was characterized based on low-temperature neutron powder diffraction.With increasing Tm content from 0 to 1,the Curie temperature of Er_(1-x)Tm_(x)Al_(2)(0≤x≤1)compounds decreases from 16.0 K to 3.6 K.For Er_(0.7)Tm_(0.3)Al_(2) compound,it showed the largest low-field magnetic entropy change(–SM)with the peak value of 17.2 and 25.7 J/(kg K)for 0–1 T and 0–2 T,respectively.The(–SM)max up to 17.2 J/(kg K)of Er0.7Tm0.3Al2 compound for 0–1 T is the largest among the intermetallic magnetocaloric materials ever reported at temperatures below 20 K.The peak value of adiabatic temperature change(Tad)max was determined as 4.13 K and 6.87 K for 0–1 T and 0–2 T,respectively.The characteristic of second-order magnetic transitions was confirmed on basis of Arrott plots,the quantitative criterion of exponent n,rescaled universal curves,and the mean-field theory criterion.The outstanding low-field MCE performance with low working temperatures indicates that Er_(1-x)Tm_(x)Al_(2)(0≤x≤1)compounds are promising candidates for magnetic cooling materials at liquid hydrogen and liquid helium temperatures.
基金the National Natural Sci-ence Foundation of China(Grant No.52071197)the National Science Foundation for Distinguished Young Scholars(Grant No.51925605)the National Science Foundation for Excellent Young Scholars(Grant No.52222107).
文摘Magnetic refrigeration based on the magnetocaloric effect(MCE)of magnetic solids has been considered as an emerging technology for hydrogen liquefaction.However,the lack of high-performance materials has slowed the development of any practical applications.Here,we present a family of rare-earth cobalt nickel-based magnetocaloric materials,namely Dy_(1-x)Ho_(x)CoNi and Ho_(1-x)Er_(x)CoNi compounds,and system-atically investigated their structural and magnetic properties as well as the MCE and magnetocaloric per-formance.All of these compounds crystallize in the C15-type Laves-phase structure and undergo typi-cal second-order magnetic phase transition(MPT).The change in magnetism and the MPT temperature for the Dy_(1-x)Ho_(x)CoNi and Ho_(1-x)Er_(x)CoNi compounds originate from the exchange interactions between nearest-neighbor RE 3+ion pairs.No hysteresis magnetocaloric effect was achieved,and the MPT tem-perature of these compounds could be tuned from the liquefaction temperature of nitrogen(∼77 K)to hydrogen(∼20 K)by adjusting the ratio of rare-earth elements.This study’s findings indicate that theDy_(1-x)Ho_(x)CoNi and Ho_(1-x)Er_(x)CoNi compounds are of potential for practical magnetic refrigeration applica-tions in the field of hydrogen liquefaction.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.5137102611274357+1 种基金and 51327806)the Fundamental Research Funds for the Central Universities(Grant Nos.FRF-TP-14-011A2 and FRF-TP-15-002A3)
文摘The magnetocaloric effect（MCE） of RT Si and RT Al systems with R = Gd–Tm, T = Fe–Cu and Pd, which have been widely investigated in recent years, is reviewed. It is found that these RT X compounds exhibit various crystal structures and magnetic properties, which then result in different MCE. Large MCE has been observed not only in the typical ferromagnetic materials but also in the antiferromagnetic materials. The magnetic properties have been studied in detail to discuss the physical mechanism of large MCE in RT X compounds. Particularly, some RT X compounds such as Er Fe Si,Ho Cu Si, Ho Cu Al exhibit large reversible MCE under low magnetic field change, which suggests that these compounds could be promising materials for magnetic refrigeration in a low temperature range.
基金supported by the National Natural Science Foundation of China(51741105)
文摘The investigation on Curie temperature and magnetocaloric effect of the FeCrMoCBYNi bulk metallic glass(BMG) with different crystallized phases was carried out by XRD,TEM and PPMS. The experimental results show that the Curie temperature(T_c) of Fe_(45)Cr_(15)Mo_(14)C_(15)B_6 Y_2 Ni_3 BMG with different annealing condition reaches a highest value of 95 K. The value of magnetic entropy change △S_M(T) of Sample 3 reaches a maxima of 0.48 J/(kg·K) at Tc temperature, which result from the interaction among the precipitated phases of(Fe,Cr)_(23)(C,B)_6, Fe_3 Mo_3 C and residual amorphous phase. Based on the experiment results, it can be obtained that the Curie temperature, magnetocaloric effect can reach their optimal value at low temperature, when the content of amorphous phase and precipitated phases type run up to certain value. The magnetic properties of Sample 1 with full amorphous phase and Sample 4 with full crystalline phase will both decrease.
文摘The research on magnetocaloric materials for applications concentrates,among other,on two parameters:the ordering temperature and the value of the magnetocaloric effect(MCE).The optimization consists in tuning the former without significant drop in the latter.These studies report on the magnetic susceptibility,magnetization curves,heat capacity and magnetocaloric effect measurements for compositionally and structurally modified Gd5Si4 compound.The modifications are based on the doping of the parent compound with an excess Gd atoms and substitution of Si with B as well as on the dimensional effect studied by mechanical milling.Moreover,composite samples of the type Gd:Gd5Si2Ge2 were investigated revealing the influence of the intergranular interactions on the magnetocaloric properties.It appears that these interventions enable a controllable steering of the ordering temperature shifting it towards the room temperature with,in some cases,minor reduction of the parameters characterizing MCE.
基金Project supported by the National Natural Science Foundation of China(91963123)the State Key Laboratory of Solidification Processing in NWPU(SKLSP202020)+1 种基金the Ten Thousand Talents Plan of Zhejiang Province of China(2018R52003)the Fundamental Research Funds for the Provincial University of Zhejiang(GK199900299012-022)。
文摘Three binuclear rare earth based complexes combining RE ions with semirigid tricarboxylic ligand(H_(3)L).namely,[RE_(2)(L)_(2)(DMF)_(4)][RE=Gd,Tb,and Dy;H_(3)L=5-((4-Carboxybenzyl)oxy)isophthalic acid;DMF=N,N-dimethylformamide]complexes,were fabricated success fully.The RE_(2)(L)_(2)(DMF)_(4) co mplexe s consist of two central RE ions with the same coordination environment which were connected by two tridentate bridging carboxylic groups and two syn-syn bidentate bridging carboxylic groups originating from the L^(3-)ligands to form the{RE_(2)}dimeric unit,and thus provides the basis for further constructing a dense three-dimensional(3 D)network structure.Moreover,the present RE_(2)(L)_(2)(DMF)_(4) complexes can be described by a topology diagram with the topology point symbol of{4^(2)·6}_(2){4^(4)·6^(2)·8^(7)·10^(2)}.Weak antiferromagnetic(AFM)coupling between the adjacent RE ions for all the present complexes was found according to the magnetic calculations.The observed significant cryogenic magnetocaloric effect(MCE)with the maximum magnetic entropy change-ΔS_(M)^(max) to be 26.3 J/(kg·K)withΔH=7 T in Gd_(2)(L)_(2)(DMF)_(4) complex makes it competitive for the cryogenic magnetic refrigerant.Moreover,the slow magnetic relaxation behavior at 0.2 T dc field with an obvious large U_(eff)/k=45(4)K and τ_(0)=6.5(2)×10^(-10)s was confirmed in Dy_(2)(L)_(2)(DMF)_(4)complex.This work not only provides an effective strategy for obtaining molecular materials with high MCE,but also confirms that tricarboxylate ligands are the ideal choice for constructing stable high dimensional geometric structures.
