Magnetic properties and magnetic entropy changes in LaFe11.5Si1.5 have been investigated by partially substituting Pr by La. It is found that La1-xPrxFe11.5Si1.5 compounds remain cubic NaZn13-type structures even when...Magnetic properties and magnetic entropy changes in LaFe11.5Si1.5 have been investigated by partially substituting Pr by La. It is found that La1-xPrxFe11.5Si1.5 compounds remain cubic NaZn13-type structures even when the Pr content is increased to 0.5, i.e. x = 0.5. Substitution of Pr for La leads to a reduction in both the crystal constant and the Curie temperature. A stepwise magnetic behaviour in the isothermal magnetization curves is observed, indicating that the characteristic of the itinerant electron metamagnetic （IEM） transition above Tc becomes more prominent with the Pr content increasing. As a result, the magnetic entropy change is remarkably enhanced from 23.0 to 29.4 J/kg·K as the field changes from 0 to 5T, with the value of x increasing from 0 to 0.5. It is more attractive that the magnetic entropy changes for all samples are shaped into high plateaus in a wide range of temperature, which is highly favourable for Ericsson-type magnetic refrigeration.展开更多
Magnetoresistances and magnetic entropy changes in NaZn13-type compounds La（Fel-xCox）11.9Si1.1 （x=0.04, 0.06, and 0.08） with Curie temperatures of 243 K, 274 K, and 301 K, respectively, are studied. The ferromagne...Magnetoresistances and magnetic entropy changes in NaZn13-type compounds La（Fel-xCox）11.9Si1.1 （x=0.04, 0.06, and 0.08） with Curie temperatures of 243 K, 274 K, and 301 K, respectively, are studied. The ferromagnetic ordering is accompanied by a negative lattice expansion. Large magnetic entropy changes in a wide temperature range from ～230 K to ～320 K are achieved. Raising Co content increases the Curie temperature but weakens the magnetovolume effect, thereby causing a decrease in magnetic entropy change. These materials exhibit a metallic character below Tc, whereas the electrical resistance decreases abruptly and then recovers the metal-like behaviour above Tc. Application of a magnetic field retains the transitions via increasing the ferromagnetic ordering temperature. An isothermal increase in magnetic field leads to an increase in electrical resistance at temperatures near but above Tc, which is a consequence of the field-induced metamagnetic transition from a paramagnetic state to a ferromagnetic state.展开更多
A series of alloys (Gd1-xHox)5Si4(x=0, 0.05, 0.15, 0.25) have been prepared. Adiabatic temperature changes of(Gd1-xHox)5Si4 alloys is exactly investigated by a control and analysis system for ΔH=1.4 T, and the measur...A series of alloys (Gd1-xHox)5Si4(x=0, 0.05, 0.15, 0.25) have been prepared. Adiabatic temperature changes of(Gd1-xHox)5Si4 alloys is exactly investigated by a control and analysis system for ΔH=1.4 T, and the measurement results are trustworthy. Curie temperatures of these alloys are tunable in a wide temperature region, and decrease almost linearly with the increasing of Ho content. Magnetic entropy changes in the (Gd1-xHox)Si4 compounds are about 2.35 J/(kg·K) when magnetic field change are 0～1.4 T. The adiabatic temperatures of these alloys at Curie Points are larger than 1 K about 40% of that of Gd in a field change 0～1.4 T, and the curves of ΔTad are as wide as that of Gd. The relative cooling power RCP(S) or RCP(T) of these alloys are about 0.5～0.7 J·cm-3 and 42～50 K2 on the field 0～1.4 T, about 58% and 55% of that of Gd respectively. These alloys are potential magnetic refrigerants working in a refrigerator at room temperatures.展开更多
A series of Ce2-xPrxFe16.5Co0.5 alloys were prepared by arc melting under purified argon atmosphere. The structure and magnetic entropy changes in Ce2-xPrxFe16.5Co0.5 alloys were investigated by means of X-ray diffrac...A series of Ce2-xPrxFe16.5Co0.5 alloys were prepared by arc melting under purified argon atmosphere. The structure and magnetic entropy changes in Ce2-xPrxFe16.5Co0.5 alloys were investigated by means of X-ray diffraction pattern and MPMS XL-7 magnetometer. The experimental results show that the crystal structure of Ce2-xPrxFe16.5Co0.5 alloys keeps in Th2Zn17-type rhombohedral, and the Curie temperature of Ce2-xPrxFe16.5Co0.5 alloys can be shifted to room temperature around by a composition adjustment. The magnetic entropy changes (-ΔSM) in Ce2-xPrxFe16.5Co0.5 alloys are relatively large, and a platform of magnetic entropy changes appears near the temperature TC. Ce2-xPrxFe16.5Co0.5 alloys are the potential working media for magnetic refrigeration with their stable chemical properties and especially low price.展开更多
Magnetic refrigeration techniques based on the magnetocaloric effect (MCE) were demonstrated as a promising alternative to conventional vapour-cycle refrigeration.Recently, scientists focused their research on room te...Magnetic refrigeration techniques based on the magnetocaloric effect (MCE) were demonstrated as a promising alternative to conventional vapour-cycle refrigeration.Recently, scientists focused their research on room temperature magnetic refrigeration.The rare earth Gd metal is regarded as a prototype for room temperature magnetic refrigerant.Considering the various requirements in application, it is necessary to search for the magnetic refrigerant possessing qualities as good as Gd but having different Tc above or below room temperature.In this article, we report the magnetic entropy changes in Gd1 -xTx(T = Ti, Cr, Fe and Cu) alloys.With a small quantity of T atoms introduced in Gd, the Curie temperature increases.The values of magnetic entropy change in these alloys are almost the same as or a little less than that of Gd.But the refrigerant capacities of these alloys are obviously larger than that of Gd.All these facts suggest that Gd1-xTx(T = Ti, Cr, Fe and Cu) alloys may be good refrigerants for room temperature magnetic refrigeration.展开更多
We investigate the carrier, phonon, and spin dynamics in the ferromagnetic semiconductor(In,Fe)Sb using ultrafast optical pump-probe spectroscopy. We discover two anomalies near T^(*)(~40 K) and T^(†)(~200 K) in the p...We investigate the carrier, phonon, and spin dynamics in the ferromagnetic semiconductor(In,Fe)Sb using ultrafast optical pump-probe spectroscopy. We discover two anomalies near T^(*)(~40 K) and T^(†)(~200 K) in the photoexcited carrier dynamics, which can be attributed to the electron-spin and spin-lattice scattering processes influenced by the magnetic phase transition and modifications in magnetic anisotropy. The magnetization change can be revealed by the dynamics of coherent acoustic phonon. We also observe abrupt changes in the photoinduced spin dynamics near T^(*)and T^(†), which not only illustrate the spin-related scatterings closely related to the long-range magnetic order, but also reveal the D'yakonov–Perel and Elliott–Yafet mechanisms dominating at temperatures below and above T^(†), respectively. Our findings provide important insights into the nonequilibrium properties of the photoexcited(In,Fe)Sb.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
With the intention to explore excellent magnetocaloric materials, the intermetallic compound GdPd was synthesized by arc melting and heat treatment. The microstructure, magnetic and magnetocaloric properties of the in...With the intention to explore excellent magnetocaloric materials, the intermetallic compound GdPd was synthesized by arc melting and heat treatment. The microstructure, magnetic and magnetocaloric properties of the intermetallic compound of GdPd were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and the physical property measurement system（PPMS）. A large reversible magnetocaloric effect is observed in GdPd accompanied by a second order magnetic phase transition from paramagnetism to ferromagnetism at ～39 K. The paramagnetic Curie temperature（θp） and the effective magnetic moment（μ（eff））are determined to be 34.7 K and 8.12 μB/Gd,respectively. The maximum entropy change（｜△SM（Max）｜） and the relative cooling power（RCP） under a field change of 5 T are estimated to be 20.14 J/（kg·K） and 433 J/kg, respectively. The giant reversible magnetocaloric effects（both the large△SM and the high RCP） together with the absence of thermal and field hysteresis make the GdPd compound an attractive candidate for low-temperature magnetic refrigeration.展开更多
Effect of impurity phase（α-Fe phase and La-rich phase） on corrosion resistance and magnetic entropy change of LaFe_（11.3）Co_（0.4）Si_（1.3）C_（0.15） compound was studied using scanning electron microscopy, pot...Effect of impurity phase（α-Fe phase and La-rich phase） on corrosion resistance and magnetic entropy change of LaFe_（11.3）Co_（0.4）Si_（1.3）C_（0.15） compound was studied using scanning electron microscopy, potentiodynamic polarization, electrochemical impedance spectroscopy techniques and magnetism testing. With the decrease of impurity phase, the corrosion resistance of LaFe_（11.3）Co_（0.4）Si_（1.3）C_（0.15） compound was first enhanced and then slightly impaired. Corrosion resistance could be significantly improved by the decrease of α-Fe phase. However, the matrix phase was corroded if the La-rich phase as anode was too few. This caused the corrosion resistance to decrease slightly. After immersing the sample in distilled water for 15 d, -？S_（max） of the samples annealed for 3, 12 h, 3 and 7 d decreased about 50%, 41%, 16% and 17%, respectively.展开更多
In this article, our recent progress concerning the effects of atomic substitution, magnetic field, and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed. With an incr...In this article, our recent progress concerning the effects of atomic substitution, magnetic field, and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed. With an increase of the aluminum content, the compounds exhibit successively an antiferromagnetic （AFM） state, a ferromagnetic （FM） state, and a mictomagnetic state. Furthermore, the AFM coupling of LaFe13 -xAlx can be converted to an FM one by substituting Si for A1, Co for Fe, and magnetic rare-earth R for La, or introducing interstitial C or H atoms. However, low doping levels lead to FM clusters embedded in an AFM matrix, and the resultant compounds can undergo, under appropriate applied fields, first an AFM-FM and then an FM-AFM phase transition while heated, with significant magnetic relaxation in the vicinity of the transition temperature. The Curie temperature of LaFe13-xAlx can be shifted to room temperature by choosing appropriate contents of Co, C, or H, and a strong magnetocaloric effect can be obtained around the transition temperature. For example, for the LaFel 1.5All.5Co.2Hl.o compound, the maximal entropy change reaches 13.8 J.kg-1.K-1 for a field change of 0-5 T, occurring around room temperature. It is 42% higher than that of Gd, and therefore, this compound is a promising room-temperature magnetic refrigerant.展开更多
Tb1-xTmxFeO3(x = 0.00,0.15,0.25) polycrystalline series were synthesized using a solid-state reaction.Our results show that all three prepared samples are in a distorted orthogonal structure and their space group is p...Tb1-xTmxFeO3(x = 0.00,0.15,0.25) polycrystalline series were synthesized using a solid-state reaction.Our results show that all three prepared samples are in a distorted orthogonal structure and their space group is pbnm.When the Tm3+doping amount increases,the characteristics of the spin-flip of the sample decreases following an initial increase at the beginning;the antiferromagnetic property almost reaches zero;the magnetization decreases at the beginning but increases later on.The maximum magnetic entropy change and magnetic refrigeration effect RCP are reduced at varying degrees.Under a 7 T magnetic field,the maximum magnetic entropy change,△Smax,for the three samples of Tb1-xTmxFeO3 with x=0.00,0.15,0.25 is 13.78,-9.28,and 10.69 J/(K·kg),respectively;the magnetic refrigeration capacity(RCP) is 316.85,175.2,and 297.60 J/kg,respectively.In summary,doping with the element Tm reduces △Smax and RCP of the sample.Since the maximum magnetic entropy change and the cooling capacity for the three samples are relatively large,they can be used as an alternative for magnetic refrigerants.展开更多
Our recent progress on magnetic entropy change（S） involving martensitic transition in both conventional and metamagnetic NiMn-based Heusler alloys is reviewed.For the conventional alloys,where both martensite and au...Our recent progress on magnetic entropy change（S） involving martensitic transition in both conventional and metamagnetic NiMn-based Heusler alloys is reviewed.For the conventional alloys,where both martensite and austenite exhibit ferromagnetic（FM） behavior but show different magnetic anisotropies,a positive S as large as 4.1 J·kg^-1·K^-1 under a field change of 0-0.9 T was first observed at martensitic transition temperature T M～197 K.Through adjusting the Ni：Mn：Ga ratio to affect valence electron concentration e/a,T M was successfully tuned to room temperature,and a large negative S was observed in a single crystal.The △S attained 18.0 J·kg^-1·K^-1 under a field change of 0-5 T.We also focused on the metamagnetic alloys that show mechanisms different from the conventional ones.It was found that post-annealing in suitable conditions or introducing interstitial H atoms can shift the T M across a wide temperature range while retaining the strong metamagnetic behavior,and hence,retaining large magnetocaloric effect（MCE） and magnetoresistance（MR）.The melt-spun technique can disorder atoms and make the ribbons display a B2 structure,but the metamagnetic behavior,as well as the MCE,becomes weak due to the enhanced saturated magnetization of martensites.We also studied the effect of Fe/Co co-doping in Ni 45（Co1-xFex）5 Mn36.6In13.4 metamagnetic alloys.Introduction of Fe atoms can assist the conversion of the Mn-Mn coupling from antiferromagnetic to ferromagnetic,thus maintaining the strong metamagnetic behavior and large MCE and MR.Furthermore,a small thermal hysteresis but significant magnetic hysteresis was observed around TM in Ni51Mn49-xInx metamagnetic systems,which must be related to different nucleation mechanisms of structural transition under different external perturbations.展开更多
The LaFe11.9–x Cox Si1.1 B0.25 with x=0.9 and x=0.82 compounds were synthesized from commercial purity raw materials.The magnetic property of LaFe11.9–x Cox Si1.1 B0.25 and Gd particles were tested on the reciprocat...The LaFe11.9–x Cox Si1.1 B0.25 with x=0.9 and x=0.82 compounds were synthesized from commercial purity raw materials.The magnetic property of LaFe11.9–x Cox Si1.1 B0.25 and Gd particles were tested on the reciprocating refrigerator at the same condition in order to compare the cooling capacity of the two materials.The results showed that the cooling velocity of Gd was obviously higher than that of LaFe11.9–x Cox Si1.1 B0.25.The maximum temperature span was 12.7 oC for LaFe11.0 Co0.9 Si1.1 B0.25,14.9 oC for Gd metal whose mass is the same as that of LaFe11.0 Co0.9 Si1.1 B0.25,8.1 oC for Gd metal whose volume is the same as that of LaFe11.0 Co0.9 Si1.1 B0.25.Series connection of LaFe11.0 Co0.9 Si1.1 B0.25 and LaFe11.08 Co0.82 Si1.1 B0.25 had the maximum cooling temperature span of 15.3 oC.展开更多
A low cost Gd_(34)Ni_(33)Al_(33) metallic glass with excellent magnetocaloric properties was successfully prepared in the present work.The magnetic properties of the ribbons were measured by constructing the relations...A low cost Gd_(34)Ni_(33)Al_(33) metallic glass with excellent magnetocaloric properties was successfully prepared in the present work.The magnetic properties of the ribbons were measured by constructing the relationship of magnetic entropy change(-ΔS_(m)) on temperature as well as magnetic field.The amorphous alloy shows typical magnetocaloric behaviors,large maximum-ΔS_(m)(11.06 J/(kg·K) under 5 T)and adiabatic temperature rise(4.3 K under 5 T) near 40 K,indicating that the low cost Gd_(34)Ni_(33)Al_(33) metallic glass is a good candidate material for low temperature magnetic refrigeration.展开更多
Magnetic properties and magnetocaloric effects （MCEs） of the PrSi compound were studied. The PrSi compound undergoes a second-order ferromagnetic-to-paramagnetic transition at the Curie temperature of Tc = 52 K. Lar...Magnetic properties and magnetocaloric effects （MCEs） of the PrSi compound were studied. The PrSi compound undergoes a second-order ferromagnetic-to-paramagnetic transition at the Curie temperature of Tc = 52 K. Large MCE with no magnetic hysteresis loss is observed around Tc. The maximum values of magnetic entropy change （△S） are found to be -8.6 and -15.3 J.kg^-1.K^-1 for the magnetic field changes of 0-2 T and 0-5 T, respectively. The large △S with no hysteresis makes PrSi compound a competitive candidate for magnetic refrigerant.展开更多
The unit cell volume and phase transition temperature of LaFe11.4Al1.6Cx compounds have been studied. The magnetic entropy change, refrigerant capacity and the type of magnetic phase transition are investigated in det...The unit cell volume and phase transition temperature of LaFe11.4Al1.6Cx compounds have been studied. The magnetic entropy change, refrigerant capacity and the type of magnetic phase transition are investigated in detail for LaFe11.4Al1.6Cx with x=0.1, All the LaFe11.4Al1.6Cx （x=0-0.8） compounds have the cubic NaZn13-type structure. The addition of carbon atoms brings about a considerable increase in the lattice parameter. The bulk expansion results in the change of phase transition temperature （Tc）, Tc increases from 187K to 269 K with x varying from 0.1 to 0.8, Meanwhile an increase in the lattice parameter can also cause a change of the magnetic ground state from antiferromagnetic to ferromagnetic. Large magnetic entropy change IASI is found over a large temperature range around Tc and the refrigerant capacity is about 322J/kg for LaFe11.4Al1.6C0.1. The magnetic phase transition belongs in weakly first-order one for x=0.1.展开更多
In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12...In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12）Co_7 series, R_3 Co series and RCu_2series）, which have been investigated in detail in the past several years. The R–T compounds are studied by means of magnetic measurements, heat capacity measurements, magnetoresistance measurements and neutron powder diffraction measurements. The R–T compounds show complex magnetic transitions and interesting magnetic properties.The types of magnetic transitions are investigated and confirmed in detail by multiple approaches. Especially, most of the R–T compounds undergo more than one magnetic transition, which has significant impact on the magnetocaloric effect of R–T compounds. The MCE of R–T compounds are calculated by different ways and the special shapes of MCE peaks for different compounds are investigated and discussed in detail. To improve the MCE performance of R–T compounds,atoms with large spin（S） and atoms with large total angular momentum（J） are introduced to substitute the related rare earth atoms. With the atom substitution, the maximum of magnetic entropy change（？SM）, refrigerant temperature width（Twidth）or refrigerant capacity（RC） is enlarged for some R–T compounds. In the low temperature range, binary R–T（R = Pr, Gd,Tb, Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series,R_（12）Co_7 series, R_3 Co series and RCu_2series） show excellent performance of MCE, indicating the potential application for gas liquefaction in the future.展开更多
Samarium monosulfide(SmS)is a promising material for creating thermoelectric generators(TEG),gas sensors and strain gauges.Despite the high values of the generated thermo electromotive force(TEMF)(α≈170-350μV/K),me...Samarium monosulfide(SmS)is a promising material for creating thermoelectric generators(TEG),gas sensors and strain gauges.Despite the high values of the generated thermo electromotive force(TEMF)(α≈170-350μV/K),methods for increasing the efficiency of TEGs based on SmS are of considerable interest.One of these methods can be short-term effects of magnetic fields,including pulsed ones,on these materials.The action of a pulsed magnetic field(PMF)leading to an increase in TEMF(U)of SmS ceramic samples is found.Samples that are not subjected to high frequency currents(HFC)annealing show an increase in UT of 44.54%-62.18%(from 11.9 to 17.2-19.3 mV).The conductivity(σ)of the samples is~22 Q/cm and is insensitive to short-term exposure to a PMF.Samples that undergo HFC annealing show an increase in Uof 23.47%-41.31%(from 21.3 to 26.3-30.1 mV)after exposure to a PMF.The conductivity of the samples is~15Ω^(-1)/cm and after a short exposure to the PMF is changing nonmo notonically,with an increase in the overall instability.The difference in the values of Uand a can be explained by presence of an ordered grain structure and a significant amount of the Sm_(2)O_(2)S phase in the samples subjected to HFC annealing.Possible mechanisms of the observed changes are discussed.展开更多
The phases and magnetocaloric effect in the alloys （Gd1-xNdx）Co2 with x = 0, 0.1, 0.2, 0.3, and 0.4 were investigated by X-ray diffraction analysis and magnetization measurement. The samples are single phase with a ...The phases and magnetocaloric effect in the alloys （Gd1-xNdx）Co2 with x = 0, 0.1, 0.2, 0.3, and 0.4 were investigated by X-ray diffraction analysis and magnetization measurement. The samples are single phase with a cubic MgCu2-type structure. The To decreases obviously with increasing Nd content from 404 K of the alloy with x = 0 to 272 K of the alloy with x = 0.4; forx = 0.3, the To is 296 K, which is near room temperature. In the samples （Gd1-xNdx）Co2 with x = 0.0, 0.1, 0.2, 0.3, and 0.4, the maximum magnetic entropy change is 1.471, 1.228, 1.280, 1.381 and 1.610 J·kg^-1·K^-1, respectively, in the applied field range of 0-2.0 T. The results of Arrott plots confirmed that the transition type were second order magnetic transition forx = 0, 0.3, and 0.4.展开更多
The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.5–x）Si_x（x=0.4, 0.5, 0.6, 0.7） compounds were studied by X-ray diffraction（XRD） and a sup...The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.5–x）Si_x（x=0.4, 0.5, 0.6, 0.7） compounds were studied by X-ray diffraction（XRD） and a superconducting quantum interference device magnetometer（SQUID）. The results showed that all the compounds presented cubic Na Zn13-type structure. Their Curie temperatures changed complicatedly with decreasing Al content due to changes of antiferromagnetic and ferromagnetic interaction. Under a field change from 0 to 2 T, the maximum magnetic entropy change for La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.1）Si_（0.4）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.0）Si_（0.5）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.9）Si_（0.6） and La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.8）Si_（0.7） were found to be –9.6, –4.8, –5.8 and –11.7 J/（kg·K）, respectively. Moreover, their hysteresis losses were 1.13 J/（kg·K） or less. The large magnetic entropy changed and small hysteresis losses made them potential candidates for practical magnetic refrigeration application.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No 50571112）, the National Basic Reseaxch Program of China （Grant No 2006CB601101） and the Program of Chinese Academy of Sciences （Grant No KJCX2-YW-W02）.
文摘Magnetic properties and magnetic entropy changes in LaFe11.5Si1.5 have been investigated by partially substituting Pr by La. It is found that La1-xPrxFe11.5Si1.5 compounds remain cubic NaZn13-type structures even when the Pr content is increased to 0.5, i.e. x = 0.5. Substitution of Pr for La leads to a reduction in both the crystal constant and the Curie temperature. A stepwise magnetic behaviour in the isothermal magnetization curves is observed, indicating that the characteristic of the itinerant electron metamagnetic （IEM） transition above Tc becomes more prominent with the Pr content increasing. As a result, the magnetic entropy change is remarkably enhanced from 23.0 to 29.4 J/kg·K as the field changes from 0 to 5T, with the value of x increasing from 0 to 0.5. It is more attractive that the magnetic entropy changes for all samples are shaped into high plateaus in a wide range of temperature, which is highly favourable for Ericsson-type magnetic refrigeration.
基金Project supported by the State Key Development Program for Basic Research of China （Grant No 1998061303）, the National Natural Science Foundation of China （Grant Nos 10474066 and 10174094）, and the Beijing Natural Science Foundation of China （Grant No 1012002）.
文摘Magnetoresistances and magnetic entropy changes in NaZn13-type compounds La（Fel-xCox）11.9Si1.1 （x=0.04, 0.06, and 0.08） with Curie temperatures of 243 K, 274 K, and 301 K, respectively, are studied. The ferromagnetic ordering is accompanied by a negative lattice expansion. Large magnetic entropy changes in a wide temperature range from ～230 K to ～320 K are achieved. Raising Co content increases the Curie temperature but weakens the magnetovolume effect, thereby causing a decrease in magnetic entropy change. These materials exhibit a metallic character below Tc, whereas the electrical resistance decreases abruptly and then recovers the metal-like behaviour above Tc. Application of a magnetic field retains the transitions via increasing the ferromagnetic ordering temperature. An isothermal increase in magnetic field leads to an increase in electrical resistance at temperatures near but above Tc, which is a consequence of the field-induced metamagnetic transition from a paramagnetic state to a ferromagnetic state.
文摘A series of alloys (Gd1-xHox)5Si4(x=0, 0.05, 0.15, 0.25) have been prepared. Adiabatic temperature changes of(Gd1-xHox)5Si4 alloys is exactly investigated by a control and analysis system for ΔH=1.4 T, and the measurement results are trustworthy. Curie temperatures of these alloys are tunable in a wide temperature region, and decrease almost linearly with the increasing of Ho content. Magnetic entropy changes in the (Gd1-xHox)Si4 compounds are about 2.35 J/(kg·K) when magnetic field change are 0～1.4 T. The adiabatic temperatures of these alloys at Curie Points are larger than 1 K about 40% of that of Gd in a field change 0～1.4 T, and the curves of ΔTad are as wide as that of Gd. The relative cooling power RCP(S) or RCP(T) of these alloys are about 0.5～0.7 J·cm-3 and 42～50 K2 on the field 0～1.4 T, about 58% and 55% of that of Gd respectively. These alloys are potential magnetic refrigerants working in a refrigerator at room temperatures.
基金This work was financially supported by the Natural Science Foundation of Guangdong Province (No.05300306) and the Natural Science Foundation of the Guangdong Province, China (No.C013003).
文摘A series of Ce2-xPrxFe16.5Co0.5 alloys were prepared by arc melting under purified argon atmosphere. The structure and magnetic entropy changes in Ce2-xPrxFe16.5Co0.5 alloys were investigated by means of X-ray diffraction pattern and MPMS XL-7 magnetometer. The experimental results show that the crystal structure of Ce2-xPrxFe16.5Co0.5 alloys keeps in Th2Zn17-type rhombohedral, and the Curie temperature of Ce2-xPrxFe16.5Co0.5 alloys can be shifted to room temperature around by a composition adjustment. The magnetic entropy changes (-ΔSM) in Ce2-xPrxFe16.5Co0.5 alloys are relatively large, and a platform of magnetic entropy changes appears near the temperature TC. Ce2-xPrxFe16.5Co0.5 alloys are the potential working media for magnetic refrigeration with their stable chemical properties and especially low price.
基金Project supported by the National Key Project for Basic Research ( G1999064508 ) and National Natural Science Foundation of China (50271031)
文摘Magnetic refrigeration techniques based on the magnetocaloric effect (MCE) were demonstrated as a promising alternative to conventional vapour-cycle refrigeration.Recently, scientists focused their research on room temperature magnetic refrigeration.The rare earth Gd metal is regarded as a prototype for room temperature magnetic refrigerant.Considering the various requirements in application, it is necessary to search for the magnetic refrigerant possessing qualities as good as Gd but having different Tc above or below room temperature.In this article, we report the magnetic entropy changes in Gd1 -xTx(T = Ti, Cr, Fe and Cu) alloys.With a small quantity of T atoms introduced in Gd, the Curie temperature increases.The values of magnetic entropy change in these alloys are almost the same as or a little less than that of Gd.But the refrigerant capacities of these alloys are obviously larger than that of Gd.All these facts suggest that Gd1-xTx(T = Ti, Cr, Fe and Cu) alloys may be good refrigerants for room temperature magnetic refrigeration.
基金supported by the National Key R&D Program of China (Grant No. 2024YFA1408502)the National Natural Science Foundation of China (Grant Nos. 92365102, 62027807, 12474107, and 12174383)+1 种基金the Chinese Academy of Sciences project for Yong Scientists in Basic Research (Grant No. YSBR-030)the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2024A1515011600)。
文摘We investigate the carrier, phonon, and spin dynamics in the ferromagnetic semiconductor(In,Fe)Sb using ultrafast optical pump-probe spectroscopy. We discover two anomalies near T^(*)(~40 K) and T^(†)(~200 K) in the photoexcited carrier dynamics, which can be attributed to the electron-spin and spin-lattice scattering processes influenced by the magnetic phase transition and modifications in magnetic anisotropy. The magnetization change can be revealed by the dynamics of coherent acoustic phonon. We also observe abrupt changes in the photoinduced spin dynamics near T^(*)and T^(†), which not only illustrate the spin-related scatterings closely related to the long-range magnetic order, but also reveal the D'yakonov–Perel and Elliott–Yafet mechanisms dominating at temperatures below and above T^(†), respectively. Our findings provide important insights into the nonequilibrium properties of the photoexcited(In,Fe)Sb.
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 Basic Research Program of China(2014CB643703)the National Key Research and Development Program of China(2016YFB0700901)the National Natural Science Foundation of China(51261004,51461012)
文摘With the intention to explore excellent magnetocaloric materials, the intermetallic compound GdPd was synthesized by arc melting and heat treatment. The microstructure, magnetic and magnetocaloric properties of the intermetallic compound of GdPd were investigated by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and the physical property measurement system（PPMS）. A large reversible magnetocaloric effect is observed in GdPd accompanied by a second order magnetic phase transition from paramagnetism to ferromagnetism at ～39 K. The paramagnetic Curie temperature（θp） and the effective magnetic moment（μ（eff））are determined to be 34.7 K and 8.12 μB/Gd,respectively. The maximum entropy change（｜△SM（Max）｜） and the relative cooling power（RCP） under a field change of 5 T are estimated to be 20.14 J/（kg·K） and 433 J/kg, respectively. The giant reversible magnetocaloric effects（both the large△SM and the high RCP） together with the absence of thermal and field hysteresis make the GdPd compound an attractive candidate for low-temperature magnetic refrigeration.
基金supported by the National Natural Science Foundation of China(51571018,51371026)the National High Technology Research and Development Program of China(2011AA03A404)
文摘Effect of impurity phase（α-Fe phase and La-rich phase） on corrosion resistance and magnetic entropy change of LaFe_（11.3）Co_（0.4）Si_（1.3）C_（0.15） compound was studied using scanning electron microscopy, potentiodynamic polarization, electrochemical impedance spectroscopy techniques and magnetism testing. With the decrease of impurity phase, the corrosion resistance of LaFe_（11.3）Co_（0.4）Si_（1.3）C_（0.15） compound was first enhanced and then slightly impaired. Corrosion resistance could be significantly improved by the decrease of α-Fe phase. However, the matrix phase was corroded if the La-rich phase as anode was too few. This caused the corrosion resistance to decrease slightly. After immersing the sample in distilled water for 15 d, -？S_（max） of the samples annealed for 3, 12 h, 3 and 7 d decreased about 50%, 41%, 16% and 17%, respectively.
基金Project supported by the National Natural Science Foundation of Chinathe Key Research Program of the Chinese Academy of Sciences+1 种基金the National Basic Research Program of Chinathe National High Technology Research and Development Program of China
文摘In this article, our recent progress concerning the effects of atomic substitution, magnetic field, and temperature on the magnetic and magnetocaloric properties of the LaFe13-xAlx compounds are reviewed. With an increase of the aluminum content, the compounds exhibit successively an antiferromagnetic （AFM） state, a ferromagnetic （FM） state, and a mictomagnetic state. Furthermore, the AFM coupling of LaFe13 -xAlx can be converted to an FM one by substituting Si for A1, Co for Fe, and magnetic rare-earth R for La, or introducing interstitial C or H atoms. However, low doping levels lead to FM clusters embedded in an AFM matrix, and the resultant compounds can undergo, under appropriate applied fields, first an AFM-FM and then an FM-AFM phase transition while heated, with significant magnetic relaxation in the vicinity of the transition temperature. The Curie temperature of LaFe13-xAlx can be shifted to room temperature by choosing appropriate contents of Co, C, or H, and a strong magnetocaloric effect can be obtained around the transition temperature. For example, for the LaFel 1.5All.5Co.2Hl.o compound, the maximal entropy change reaches 13.8 J.kg-1.K-1 for a field change of 0-5 T, occurring around room temperature. It is 42% higher than that of Gd, and therefore, this compound is a promising room-temperature magnetic refrigerant.
基金the National Natural Science Foundation of China(11164019,51562032,61565013)Inner Mongolia Natural Science Foundation of China(2015MS0101,2015MS0109)+2 种基金Inner Mongolia Institute of Science and Technology Key Project Fund(NJZZ11166,NJZY16237,NJZY12202)Board Project(201522011)Natural Science Foundation of Henan Province(182300410248)。
文摘Tb1-xTmxFeO3(x = 0.00,0.15,0.25) polycrystalline series were synthesized using a solid-state reaction.Our results show that all three prepared samples are in a distorted orthogonal structure and their space group is pbnm.When the Tm3+doping amount increases,the characteristics of the spin-flip of the sample decreases following an initial increase at the beginning;the antiferromagnetic property almost reaches zero;the magnetization decreases at the beginning but increases later on.The maximum magnetic entropy change and magnetic refrigeration effect RCP are reduced at varying degrees.Under a 7 T magnetic field,the maximum magnetic entropy change,△Smax,for the three samples of Tb1-xTmxFeO3 with x=0.00,0.15,0.25 is 13.78,-9.28,and 10.69 J/(K·kg),respectively;the magnetic refrigeration capacity(RCP) is 316.85,175.2,and 297.60 J/kg,respectively.In summary,doping with the element Tm reduces △Smax and RCP of the sample.Since the maximum magnetic entropy change and the cooling capacity for the three samples are relatively large,they can be used as an alternative for magnetic refrigerants.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 51271196,11274357,and 51021061)the Key Research Program of the Chinese Academy of Sciences+1 种基金the National Basic Research Program of China (Grant No. 2010CB833102)the Hi-Tech Research and Development Program of China (Grant No. 2011AA03A404)
文摘Our recent progress on magnetic entropy change（S） involving martensitic transition in both conventional and metamagnetic NiMn-based Heusler alloys is reviewed.For the conventional alloys,where both martensite and austenite exhibit ferromagnetic（FM） behavior but show different magnetic anisotropies,a positive S as large as 4.1 J·kg^-1·K^-1 under a field change of 0-0.9 T was first observed at martensitic transition temperature T M～197 K.Through adjusting the Ni：Mn：Ga ratio to affect valence electron concentration e/a,T M was successfully tuned to room temperature,and a large negative S was observed in a single crystal.The △S attained 18.0 J·kg^-1·K^-1 under a field change of 0-5 T.We also focused on the metamagnetic alloys that show mechanisms different from the conventional ones.It was found that post-annealing in suitable conditions or introducing interstitial H atoms can shift the T M across a wide temperature range while retaining the strong metamagnetic behavior,and hence,retaining large magnetocaloric effect（MCE） and magnetoresistance（MR）.The melt-spun technique can disorder atoms and make the ribbons display a B2 structure,but the metamagnetic behavior,as well as the MCE,becomes weak due to the enhanced saturated magnetization of martensites.We also studied the effect of Fe/Co co-doping in Ni 45（Co1-xFex）5 Mn36.6In13.4 metamagnetic alloys.Introduction of Fe atoms can assist the conversion of the Mn-Mn coupling from antiferromagnetic to ferromagnetic,thus maintaining the strong metamagnetic behavior and large MCE and MR.Furthermore,a small thermal hysteresis but significant magnetic hysteresis was observed around TM in Ni51Mn49-xInx metamagnetic systems,which must be related to different nucleation mechanisms of structural transition under different external perturbations.
基金supported by National High Technology Research and Development Program of China(2011AA03A404)International Cooperation Program(2011DFA53230)+1 种基金National Natural Science Foundation of China(51261001)Science Foundation of Inner Mongolia(2011MS0801)
文摘The LaFe11.9–x Cox Si1.1 B0.25 with x=0.9 and x=0.82 compounds were synthesized from commercial purity raw materials.The magnetic property of LaFe11.9–x Cox Si1.1 B0.25 and Gd particles were tested on the reciprocating refrigerator at the same condition in order to compare the cooling capacity of the two materials.The results showed that the cooling velocity of Gd was obviously higher than that of LaFe11.9–x Cox Si1.1 B0.25.The maximum temperature span was 12.7 oC for LaFe11.0 Co0.9 Si1.1 B0.25,14.9 oC for Gd metal whose mass is the same as that of LaFe11.0 Co0.9 Si1.1 B0.25,8.1 oC for Gd metal whose volume is the same as that of LaFe11.0 Co0.9 Si1.1 B0.25.Series connection of LaFe11.0 Co0.9 Si1.1 B0.25 and LaFe11.08 Co0.82 Si1.1 B0.25 had the maximum cooling temperature span of 15.3 oC.
基金the National Natural Science Foundation of China(51671119,51701003,51871139)。
文摘A low cost Gd_(34)Ni_(33)Al_(33) metallic glass with excellent magnetocaloric properties was successfully prepared in the present work.The magnetic properties of the ribbons were measured by constructing the relationship of magnetic entropy change(-ΔS_(m)) on temperature as well as magnetic field.The amorphous alloy shows typical magnetocaloric behaviors,large maximum-ΔS_(m)(11.06 J/(kg·K) under 5 T)and adiabatic temperature rise(4.3 K under 5 T) near 40 K,indicating that the low cost Gd_(34)Ni_(33)Al_(33) metallic glass is a good candidate material for low temperature magnetic refrigeration.
基金financially supported by the National Natural Science Foundation of China(No.11274357)the Hi-Tech Research and Development Program of China(No.2011AA03A404)
文摘Magnetic properties and magnetocaloric effects （MCEs） of the PrSi compound were studied. The PrSi compound undergoes a second-order ferromagnetic-to-paramagnetic transition at the Curie temperature of Tc = 52 K. Large MCE with no magnetic hysteresis loss is observed around Tc. The maximum values of magnetic entropy change （△S） are found to be -8.6 and -15.3 J.kg^-1.K^-1 for the magnetic field changes of 0-2 T and 0-5 T, respectively. The large △S with no hysteresis makes PrSi compound a competitive candidate for magnetic refrigerant.
基金Project supported by the State Key Program of Basic Research of China （Grant No 2006CB601101）, and the National Natural Science Foundation of China （ Grant No 50271082）.
文摘The unit cell volume and phase transition temperature of LaFe11.4Al1.6Cx compounds have been studied. The magnetic entropy change, refrigerant capacity and the type of magnetic phase transition are investigated in detail for LaFe11.4Al1.6Cx with x=0.1, All the LaFe11.4Al1.6Cx （x=0-0.8） compounds have the cubic NaZn13-type structure. The addition of carbon atoms brings about a considerable increase in the lattice parameter. The bulk expansion results in the change of phase transition temperature （Tc）, Tc increases from 187K to 269 K with x varying from 0.1 to 0.8, Meanwhile an increase in the lattice parameter can also cause a change of the magnetic ground state from antiferromagnetic to ferromagnetic. Large magnetic entropy change IASI is found over a large temperature range around Tc and the refrigerant capacity is about 322J/kg for LaFe11.4Al1.6C0.1. The magnetic phase transition belongs in weakly first-order one for x=0.1.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11274357,51501005,51590880,and 11674008)the Fundamental Research Funds for the Central Universities,China(Grant No.FRF-TP-15-010A1)+1 种基金the China Postdoctoral Science Foundation(Grant No.2016M591071)the Key Research Program of the Chinese Academy of Sciences(Grant No.KJZD-EW-M05)
文摘In this paper, we review the magnetic properties and magnetocaloric effects（MCE） of binary R–T（R = Pr, Gd, Tb,Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series, R_（12）Co_7 series, R_3 Co series and RCu_2series）, which have been investigated in detail in the past several years. The R–T compounds are studied by means of magnetic measurements, heat capacity measurements, magnetoresistance measurements and neutron powder diffraction measurements. The R–T compounds show complex magnetic transitions and interesting magnetic properties.The types of magnetic transitions are investigated and confirmed in detail by multiple approaches. Especially, most of the R–T compounds undergo more than one magnetic transition, which has significant impact on the magnetocaloric effect of R–T compounds. The MCE of R–T compounds are calculated by different ways and the special shapes of MCE peaks for different compounds are investigated and discussed in detail. To improve the MCE performance of R–T compounds,atoms with large spin（S） and atoms with large total angular momentum（J） are introduced to substitute the related rare earth atoms. With the atom substitution, the maximum of magnetic entropy change（？SM）, refrigerant temperature width（Twidth）or refrigerant capacity（RC） is enlarged for some R–T compounds. In the low temperature range, binary R–T（R = Pr, Gd,Tb, Dy, Ho, Er, Tm; T = Ga, Ni, Co, Cu） intermetallic compounds（including RGa series, RNi series,R_（12）Co_7 series, R_3 Co series and RCu_2series） show excellent performance of MCE, indicating the potential application for gas liquefaction in the future.
基金Project supported by the Ministry of Science and Higher Education within the State assignment FSRC"Crystallography and Photonics"RAS。
文摘Samarium monosulfide(SmS)is a promising material for creating thermoelectric generators(TEG),gas sensors and strain gauges.Despite the high values of the generated thermo electromotive force(TEMF)(α≈170-350μV/K),methods for increasing the efficiency of TEGs based on SmS are of considerable interest.One of these methods can be short-term effects of magnetic fields,including pulsed ones,on these materials.The action of a pulsed magnetic field(PMF)leading to an increase in TEMF(U)of SmS ceramic samples is found.Samples that are not subjected to high frequency currents(HFC)annealing show an increase in UT of 44.54%-62.18%(from 11.9 to 17.2-19.3 mV).The conductivity(σ)of the samples is~22 Q/cm and is insensitive to short-term exposure to a PMF.Samples that undergo HFC annealing show an increase in Uof 23.47%-41.31%(from 21.3 to 26.3-30.1 mV)after exposure to a PMF.The conductivity of the samples is~15Ω^(-1)/cm and after a short exposure to the PMF is changing nonmo notonically,with an increase in the overall instability.The difference in the values of Uand a can be explained by presence of an ordered grain structure and a significant amount of the Sm_(2)O_(2)S phase in the samples subjected to HFC annealing.Possible mechanisms of the observed changes are discussed.
基金the National Natu-ral Science Foundation of China (No. 50371058)
文摘The phases and magnetocaloric effect in the alloys （Gd1-xNdx）Co2 with x = 0, 0.1, 0.2, 0.3, and 0.4 were investigated by X-ray diffraction analysis and magnetization measurement. The samples are single phase with a cubic MgCu2-type structure. The To decreases obviously with increasing Nd content from 404 K of the alloy with x = 0 to 272 K of the alloy with x = 0.4; forx = 0.3, the To is 296 K, which is near room temperature. In the samples （Gd1-xNdx）Co2 with x = 0.0, 0.1, 0.2, 0.3, and 0.4, the maximum magnetic entropy change is 1.471, 1.228, 1.280, 1.381 and 1.610 J·kg^-1·K^-1, respectively, in the applied field range of 0-2.0 T. The results of Arrott plots confirmed that the transition type were second order magnetic transition forx = 0, 0.3, and 0.4.
基金Project supported by the Science and Technology Development Fund of Higher Education of Tianjin,China(20130301)the Tianjin Research Program of Application Foundation and Advanced Technology,China(14JCQNJC4000)the National Natural Science Foundation of China(11604242)
文摘The microstructure, magnetic entropy changes, hysteresis and magnetic properties of La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.5–x）Si_x（x=0.4, 0.5, 0.6, 0.7） compounds were studied by X-ray diffraction（XRD） and a superconducting quantum interference device magnetometer（SQUID）. The results showed that all the compounds presented cubic Na Zn13-type structure. Their Curie temperatures changed complicatedly with decreasing Al content due to changes of antiferromagnetic and ferromagnetic interaction. Under a field change from 0 to 2 T, the maximum magnetic entropy change for La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.1）Si_（0.4）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（1.0）Si_（0.5）, La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.9）Si_（0.6） and La_（0.8）Ce_（0.2）Fe_（11.5）Al_（0.8）Si_（0.7） were found to be –9.6, –4.8, –5.8 and –11.7 J/（kg·K）, respectively. Moreover, their hysteresis losses were 1.13 J/（kg·K） or less. The large magnetic entropy changed and small hysteresis losses made them potential candidates for practical magnetic refrigeration application.
