摘要
具有正交Ho_(6)Co_(2)Ga型晶体结构的富稀土金属间化合物因其具备独特的磁性能而被关注,但它们的磁有序、磁相变类型以及磁热性能尚未见系统报道.本文通过对RE_(6)Co_(2)Ga化合物中的稀土元素类型的调控,实现了材料相变类型从反铁磁(AF)到顺磁(PM)的变磁调控为铁磁(FM)到顺磁(PM)的转变.此外,通过实验观察结合密度泛函理论(DFT)计算证明了Gd_(6)Co_(2)Ga的基态为铁磁态.利用磁热效应的场依赖性关系结合Banerjee准则的判断标准研究表明,Ho_(6)Co_(2)Ga和Dy_(6)Co_(2)Ga同时具备二级相变和一级相变特征,而在Gd_(6)Co_(2)Ga中只存在二级相变.在0-5 T的磁场变化下,Ho_(6)Co_(2)Ga和Gd_(6)Co_(2)Ga的磁熵变分别在26和75 K附近达到最大值10.1和9.1J kg^(-1)K^(-1),而这两个温度分别接近于H_(2)液化和N_(2)液化温度.优异的磁热性能使得RE_(6)Co_(2)Ga体系在低温磁制冷领域具有潜在的应用前景.
Rare-earth(RE)rich intermetallics crystallizing in orthorhombic Ho_(6)Co_(2)Ga-type crystal structure exhibit peculiar magnetic properties that are not widely reported for their magnetic ordering,order of magnetic phase transition,and related magnetocaloric behavior.By tuning the type of RE element in RE_(6)Co_(2)Ga(RE=Ho,Dy or Gd)compounds,metamagnetic anti-to-paramagnetic(AF to PM)phase transitions could be tuned to ferro-to-paramagnetic(FM to PM)phase transitions.Furthermore,the FM ground state for Gd_(6)Co_(2)Ga is confirmed by density functional theory calculations in addition to experimental observations.The field dependence magnetocaloric and Banerjee’s criteria demonstrate that Ho_(6)Co_(2)Ga and Dy_(6)Co_(2)Ga undergo a first-order phase transition in addition to a second-order phase transition,whereas only the latter is observed for Gd_(6)Co_(2)Ga.The two extreme alloys of the series,Ho_(6)Co_(2)Ga and Gd_(6)Co_(2)Ga,show maximum isothermal entropy change(|ΔS_(iso)^(max)(5T)|)of 10.1 and 9.1 J kg^(-1)K^(-1)at 26 and 75 K,close to H_(2)and N_(2)liquefaction,respectively.This outstanding magnetocaloric effect performance makes the RE6 Co_(2)Ga series of potential for cryogenic magnetic refrigeration applications.
作者
郭丹
Luis M.Moreno-Ramírez
Carlos Romero-Muñiz
张义坤
Jia-Yan Law
Victorino Franco
王江
任忠鸣
Dan Guo;Luis M.Moreno-Ramírez;Carlos Romero-Muñiz;Yikun Zhang;Jia-Yan Law;Victorino Franco;Jiang Wang;Zhongming Ren(State Key Laboratory of Advanced Special Steels,Shanghai Key Laboratory of Advanced Ferrometallurgy,School of Materials Science and Engineering,Shanghai University,Shanghai 200072,China;Departamento de Física de la Materia Condensada,ICMS-CSIC,Universidad de Sevilla,P.O.Box 1065,Sevilla 41080,Spain;Department of Physical,Chemical and Natural Systems,Universidad Pablo de Olavide,Sevilla E-41013,Spain;Departamento de Física Aplicada I,Universidad de Sevilla,Sevilla E-41012,Spain)
基金
the National Natural Science Foundation of China(52071197)
the Science and Technology Commission of Shanghai Municipality(19ZR1418300 and 19DZ2270200)
AEI/FEDER-UE(PID2019-105720RB-I00)
US/JUNTA/FEDER-UE(US-1260179)
Consejería de Economía,Conocimiento,Empresas y Universidad de la Junta de Andalucía(P18-RT-746)
the support provided by China Scholarship Council(CSC)of the Ministry of Education,China(202006890050)。