CaBaCo_(4)O_(7)has been widely studied because of its distinctive structure and magnetic properties.This study examined the influence of different cooling atmospheres on the structure,magnetic properties,and dielectri...CaBaCo_(4)O_(7)has been widely studied because of its distinctive structure and magnetic properties.This study examined the influence of different cooling atmospheres on the structure,magnetic properties,and dielectric behavior of CaBaCo_(4)O_(7).Samples were cooled under different atmospheric conditions to assess these influences.Our findings indicate that reduced oxygen content leads to increased lattice distortion.Since oxygen atoms play a crucial role in mediating magnetic exchange,oxygen deficiency disrupts long-range magnetic order and promotes short-range antiferromagnetic interactions.Additionally,the cooling atmosphere significantly impacts grain size,thereby affecting the dielectric constant and dielectric loss.In the argon-cooled CaBaCo_(4)O_(7)(Ar)sample,oxygen deficiency reduced dielectric permittivity and increased dielectric loss.展开更多
Cellular structures,distinguished by their porous characteristics,are frequently adopted in designs aimed at impact isolation,owing to their lightweight attributes and exceptional ability to absorb energy during impac...Cellular structures,distinguished by their porous characteristics,are frequently adopted in designs aimed at impact isolation,owing to their lightweight attributes and exceptional ability to absorb energy during impact events.Lattice structures often rely on plastic deformation to absorb energy.However,in applications such as sports protection and robotic grasping,there exists a requirement for a reusable structure designed to isolate impacts,which can be effectively achieved by three-dimensional flexible lattice structures.In this work,a theoretical calculation method for soft lattice structures is proposed,and in light of this method,a three-dimensional soft lattice structure aimed at isolating impacts has been carefully designed.The predictive theory for the quasistatic mechanical properties,including stiffness and buckling strength for three-dimensional soft lattice structures is described.On the basis of the quasizero stiffness characteristics inherent in body-centered cubic,octahedral,and regular diamond structures,a soft impact isolation structure is designed.The soft structure,fabricated with thermoplastic polyurethane material,demonstrated a peak impact isolation efficiency of 83%,despite possessing a thickness of 24 mm described.The work provides a novel design methodology for three-dimensional soft lattice structures and supports the development of reusable impact isolation structures for applications such as reconfigurable robots and space capture missions.展开更多
Saturation magnetization,magneto-crystalline anisotropy field,and dielectric properties are closely related to microwave devices applied at different frequencies.For regulating the magnetic and dielectric properties o...Saturation magnetization,magneto-crystalline anisotropy field,and dielectric properties are closely related to microwave devices applied at different frequencies.For regulating the magnetic and dielectric properties of W-type barium ferrites,single-phase BaMe_(2)Fe_(16)O_(27)(Me=Fe,Mn,Zn,Ni,Co) with different Me ions were synthesized by the high-temperature solid-state method.The saturation magnetization(Ms) range from 47.77 emu/g to 95.34 emu/g and the magnetic anisotropy field(H_a) range from 10700.60 Oe(1 Oe=79.5775 A·m^(-1)) to 13739.57 Oe,depending on the type of cation substitution in the hexagonal lattice.The dielectric permittivity and dielectric loss decrease with increasing frequency of the AC electric field in the low-frequency region,while they almost remain constant in the high-frequency region.The charac teristics of easy regulation and preparation make it a potential candidate for use in microwave device applications.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
The magnetization process and corresponding magnetization curve are usually used to analyze the coercivity mechanism of NdFe-B based sintered magnet.However,different demagnetization histories will seriously influence...The magnetization process and corresponding magnetization curve are usually used to analyze the coercivity mechanism of NdFe-B based sintered magnet.However,different demagnetization histories will seriously influence the magnetization curve,leading to an inaccurate understanding and analysis of magnetization process.In this work,we investigated the magnetization behavior of multi-main phase(MMP)magnets with thermal demagnetized and alternating current demagnetized states.Recoil curves of initial magnetization process and demagnetization process of thermal demagnetized magnets reflect the movement of domain walls inside the grains and the magnetization interaction between the grains,respectively.It is noted that the former process cannot represent the magnetization reversal of the entire magnet,which is not appropriate to analyze coercivity mechanism alone.While the recoil curves of both two processes of AC demagnetized magnets can illustrate the magnetization reversal of the entire grains and the interaction between grains.Magneto-optical Kerr microscope shows that the grains of thermal demagnetized magnets are in multi-domain states,and the grains of AC demagnetized magnets are almost in singledomain states.Domain walls of thermal demagnetized magnets move easily within the grains,which is more conducive to magnetization saturation in industrial production.In addition,the minorloops of thermal demagnetized magnets can independently represent the transition of grains from multi-domain to single-domain and the demagnetization of single-domain grains,which is equivalent to characterizing the internal interactions by recoil curves.The investigation of magnetization characteristics of MMP sintered magnets starting from different demagnetized states is helpful to further understand the internal interaction and magnetic hardening mechanism.展开更多
Ferromagnetic-structural transformation has been studied widely in MnCoGe-based materials. However, the magnetostructural transition(MST) from antiferromagnetic(AFM) orthorhombic phase to ferromagnetic(FM) hexagonal p...Ferromagnetic-structural transformation has been studied widely in MnCoGe-based materials. However, the magnetostructural transition(MST) from antiferromagnetic(AFM) orthorhombic phase to ferromagnetic(FM) hexagonal phase, which may lead to a large inverse magnetocaloric effect(MCE), has rarely been reported. Here, the introduction of Mn vacancy lowers the structural transition temperature while retains the AFM state in the orthorhombic phase, thus successfully realizing the AFM-FM MST in Mn0.95Co0.75Cu0.25Ge. Moreover, successive inverse and normal MCEs are observed around the first-order AFM-FM MST and the second-order FM-paramagnetic(PM) transition, respectively. A thermostat is proposed based on this special feature, which could release heat above the critical temperature while absorb heat below the critical temperature by simply applying the same magnetization/demagnetization cycles. This thermostat can be very useful in many applications where a constant temperature is required, such as cryostats and incubators.展开更多
Oxygen usually plays crucial roles in tuning the phase structures and functionalities of complex oxides such as high temperature superconductivity, colossal magnetoresistance, catalysis, etc. Effective and considerabl...Oxygen usually plays crucial roles in tuning the phase structures and functionalities of complex oxides such as high temperature superconductivity, colossal magnetoresistance, catalysis, etc. Effective and considerable control of the oxygen content in those functional oxides could be highly desired. Here, using perovskite manganite(La0.5Sr0.5)MnO3 as a paradigm, we develop a new pathway to synthesize the epitaxial thin films assisted by an in-situ chemical process, where the oxygen content can be precisely controlled by varying oxidative activity tuned by the atmospheric temperature(Tatm)during the growth. A hidden metal-insulator transition(MIT)emerges due to the phase competition, which is never shown in the phase diagram of this classic manganite. The oxygenmediated interaction between Mn ions together with the change of carrier density might be responsible for this emerging phase, which is compatible with the results of firstprinciple calculations. This work demonstrates that, apart from traditional cation doping, a precise modulation of anion(O2-, S2-, etc.) may provide a new strategy to control phase structures and functionalities of epitaxial compound thin films.展开更多
The discovery and study of skyrmion materials play an important role in basic frontier physics research and future information technology.The database of 196 materials,including 64 skyrmions,was established and predic...The discovery and study of skyrmion materials play an important role in basic frontier physics research and future information technology.The database of 196 materials,including 64 skyrmions,was established and predicted based on machine learning.A variety of intrinsic features are classified to optimize the model,and more than a dozen methods had been used to estimate the existence of skyrmion in magnetic materials,such as support vector machines,k-nearest neighbor,and ensembles of trees.It is found that magnetic materials can be more accurately divided into skyrmion and non-skyrmion classes by using the classification of electronic layer.Note that the rare earths are the key elements affecting the production of skyrmion.The accuracy and reliability of random undersampling bagged trees were 87.5%and 0.89,respectively,which have the potential to build a reliable machine learning model from small data.The existence of skyrmions in LaBaMnO is predicted by the trained model and verified by micromagnetic theory and experiments.展开更多
基金Project supported by the Key Research Project of Colleges and Universities of Henan Province(Grant No.23A140017)the Research Project of Department of Science and Technology of Henan Province(Grant No.242102231072)+1 种基金the National Natural Sciences Foundation of China(Grant No.52402336)the special fund of the Ningbo Institute of Materials Technology and Engineering,Chinese Academy of Sciences“New magnetic materials and structural devices for 5G communication”(Grant No.E41602QB01).
文摘CaBaCo_(4)O_(7)has been widely studied because of its distinctive structure and magnetic properties.This study examined the influence of different cooling atmospheres on the structure,magnetic properties,and dielectric behavior of CaBaCo_(4)O_(7).Samples were cooled under different atmospheric conditions to assess these influences.Our findings indicate that reduced oxygen content leads to increased lattice distortion.Since oxygen atoms play a crucial role in mediating magnetic exchange,oxygen deficiency disrupts long-range magnetic order and promotes short-range antiferromagnetic interactions.Additionally,the cooling atmosphere significantly impacts grain size,thereby affecting the dielectric constant and dielectric loss.In the argon-cooled CaBaCo_(4)O_(7)(Ar)sample,oxygen deficiency reduced dielectric permittivity and increased dielectric loss.
文摘Cellular structures,distinguished by their porous characteristics,are frequently adopted in designs aimed at impact isolation,owing to their lightweight attributes and exceptional ability to absorb energy during impact events.Lattice structures often rely on plastic deformation to absorb energy.However,in applications such as sports protection and robotic grasping,there exists a requirement for a reusable structure designed to isolate impacts,which can be effectively achieved by three-dimensional flexible lattice structures.In this work,a theoretical calculation method for soft lattice structures is proposed,and in light of this method,a three-dimensional soft lattice structure aimed at isolating impacts has been carefully designed.The predictive theory for the quasistatic mechanical properties,including stiffness and buckling strength for three-dimensional soft lattice structures is described.On the basis of the quasizero stiffness characteristics inherent in body-centered cubic,octahedral,and regular diamond structures,a soft impact isolation structure is designed.The soft structure,fabricated with thermoplastic polyurethane material,demonstrated a peak impact isolation efficiency of 83%,despite possessing a thickness of 24 mm described.The work provides a novel design methodology for three-dimensional soft lattice structures and supports the development of reusable impact isolation structures for applications such as reconfigurable robots and space capture missions.
基金Project supported by the National Natural Science Foundation of China (Grant No. 52088101)the Kunpeng Plan of Zhejiang ProvinceNingbo Top Talent Program。
文摘Saturation magnetization,magneto-crystalline anisotropy field,and dielectric properties are closely related to microwave devices applied at different frequencies.For regulating the magnetic and dielectric properties of W-type barium ferrites,single-phase BaMe_(2)Fe_(16)O_(27)(Me=Fe,Mn,Zn,Ni,Co) with different Me ions were synthesized by the high-temperature solid-state method.The saturation magnetization(Ms) range from 47.77 emu/g to 95.34 emu/g and the magnetic anisotropy field(H_a) range from 10700.60 Oe(1 Oe=79.5775 A·m^(-1)) to 13739.57 Oe,depending on the type of cation substitution in the hexagonal lattice.The dielectric permittivity and dielectric loss decrease with increasing frequency of the AC electric field in the low-frequency region,while they almost remain constant in the high-frequency region.The charac teristics of easy regulation and preparation make it a potential candidate for use in microwave device applications.
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supported by the National Natural Science Foundation of China(Grant No.52371169)the National Natural Science Foundation of China(Grant Nos.52088101,52001012,12204268,and 92263202)+6 种基金the National Key R&D Program of China(Grant No.2023YFA1610400)the“Leading Goose”R&D Program of Zhejiang Province(Grant No.2022C01110)the Challenge-led projects of China Rare Earth Group(Grant No.ZXKCJBGS-202405-06)the Young Elite Scientists Sponsorship Program by CAST(Grant No.YESS20230329)the Young Elite Scientists Sponsorship Program by BAST(Grant No.BYESS2023302)the National Key R&D Program of China(Grant Nos.2021YFB3501202,2022YFB3505201,and 2019YFA0704900)the Strategic Priority Research Program B of Chinese Academy of Sciences(Grant No.XDB33030200)。
文摘The magnetization process and corresponding magnetization curve are usually used to analyze the coercivity mechanism of NdFe-B based sintered magnet.However,different demagnetization histories will seriously influence the magnetization curve,leading to an inaccurate understanding and analysis of magnetization process.In this work,we investigated the magnetization behavior of multi-main phase(MMP)magnets with thermal demagnetized and alternating current demagnetized states.Recoil curves of initial magnetization process and demagnetization process of thermal demagnetized magnets reflect the movement of domain walls inside the grains and the magnetization interaction between the grains,respectively.It is noted that the former process cannot represent the magnetization reversal of the entire magnet,which is not appropriate to analyze coercivity mechanism alone.While the recoil curves of both two processes of AC demagnetized magnets can illustrate the magnetization reversal of the entire grains and the interaction between grains.Magneto-optical Kerr microscope shows that the grains of thermal demagnetized magnets are in multi-domain states,and the grains of AC demagnetized magnets are almost in singledomain states.Domain walls of thermal demagnetized magnets move easily within the grains,which is more conducive to magnetization saturation in industrial production.In addition,the minorloops of thermal demagnetized magnets can independently represent the transition of grains from multi-domain to single-domain and the demagnetization of single-domain grains,which is equivalent to characterizing the internal interactions by recoil curves.The investigation of magnetization characteristics of MMP sintered magnets starting from different demagnetized states is helpful to further understand the internal interaction and magnetic hardening mechanism.
基金supported by the National Key Research and Development Program of China (Grant No. 2017YFB0702704)the National Natural Science Foundation of China (Grant Nos. 51671022, and 51701130)+2 种基金the State Key Lab of Advanced Metals and Materials (Grant No. 2019-Z11)the Scientific and Technological Innovation Team Program of Foshan (Grant No. 2015IT100044)the Fundamental Research Funds for the Central Universities (Grant No. FRF-TP-18-014B1)
文摘Ferromagnetic-structural transformation has been studied widely in MnCoGe-based materials. However, the magnetostructural transition(MST) from antiferromagnetic(AFM) orthorhombic phase to ferromagnetic(FM) hexagonal phase, which may lead to a large inverse magnetocaloric effect(MCE), has rarely been reported. Here, the introduction of Mn vacancy lowers the structural transition temperature while retains the AFM state in the orthorhombic phase, thus successfully realizing the AFM-FM MST in Mn0.95Co0.75Cu0.25Ge. Moreover, successive inverse and normal MCEs are observed around the first-order AFM-FM MST and the second-order FM-paramagnetic(PM) transition, respectively. A thermostat is proposed based on this special feature, which could release heat above the critical temperature while absorb heat below the critical temperature by simply applying the same magnetization/demagnetization cycles. This thermostat can be very useful in many applications where a constant temperature is required, such as cryostats and incubators.
基金financially supported by the National Key Research and Development Program of China (2016YFA0302300)the support from the National Natural Science Foundation of China (51332001)the Fundamental Research Funds for the Central Universities (2017EYT26)
文摘Oxygen usually plays crucial roles in tuning the phase structures and functionalities of complex oxides such as high temperature superconductivity, colossal magnetoresistance, catalysis, etc. Effective and considerable control of the oxygen content in those functional oxides could be highly desired. Here, using perovskite manganite(La0.5Sr0.5)MnO3 as a paradigm, we develop a new pathway to synthesize the epitaxial thin films assisted by an in-situ chemical process, where the oxygen content can be precisely controlled by varying oxidative activity tuned by the atmospheric temperature(Tatm)during the growth. A hidden metal-insulator transition(MIT)emerges due to the phase competition, which is never shown in the phase diagram of this classic manganite. The oxygenmediated interaction between Mn ions together with the change of carrier density might be responsible for this emerging phase, which is compatible with the results of firstprinciple calculations. This work demonstrates that, apart from traditional cation doping, a precise modulation of anion(O2-, S2-, etc.) may provide a new strategy to control phase structures and functionalities of epitaxial compound thin films.
基金This work was supported by the National Natural Science Foundation of China(grant nos.52001012,52088101,and 51925605)the National Key Research and Development Program of China(2021YFB3501202)+6 种基金the Beijing Natural Science Foundation(grant no.2214070)the National Key Research and Development Program of China(2021YFB3501504,2022YFB3505201,2020YFA0711502,and 2019YFA0704900)the National Natural Science Foundation of China(grant nos.92263202 and 51971240)the Heye Health Technology Chong Ming Project(HYCMP-2022002 and HYCMP-2022003)the Natural Science Foundation of Inner Mongolia Autonomous Region(2019MS05040)the Strategic Priority Research Program B(XDB33030200)the Key Program of the Chinese Academy of Sciences(CAS)。
文摘The discovery and study of skyrmion materials play an important role in basic frontier physics research and future information technology.The database of 196 materials,including 64 skyrmions,was established and predicted based on machine learning.A variety of intrinsic features are classified to optimize the model,and more than a dozen methods had been used to estimate the existence of skyrmion in magnetic materials,such as support vector machines,k-nearest neighbor,and ensembles of trees.It is found that magnetic materials can be more accurately divided into skyrmion and non-skyrmion classes by using the classification of electronic layer.Note that the rare earths are the key elements affecting the production of skyrmion.The accuracy and reliability of random undersampling bagged trees were 87.5%and 0.89,respectively,which have the potential to build a reliable machine learning model from small data.The existence of skyrmions in LaBaMnO is predicted by the trained model and verified by micromagnetic theory and experiments.
