TmGa合金的磁性和磁相图  

Metamagnetic Transition and Magnetic Phase Diagram of TmGa Alloy

作　　者：莫兆军[1,2] 郝志红[3] 吴海珍[1] 王永杰[1] 李岚[1] 沈俊[2] 

机构地区：[1]天津理工大学材料物理研究所,天津300384 [2]中国科学院理化技术研究所低温重点实验室,北京100190 [3]天津职业大学眼视光学院,天津300410

出　　处：《稀有金属》2017年第8期884-889,共6页Chinese Journal of Rare Metals

基　　金：国家自然科学基金项目(11504266;51271192;51322605);国家重大科学仪器设备开发专项项目(2014YQ120351)资助

摘　　要：利用电弧熔炼制备出单相的TmGa化合物,TmGa显示了两个连续的相变:在11.5 K处为反铁磁到反铁磁(AFMΙ-AFMΠ)相变,在15 K处为反铁磁到顺磁(AFMΠ-PM)相变。反铁磁区域存在场诱导的反铁磁到铁磁(AFM-FM)变磁转变。虽然TmGa的基态是反铁磁,但是当在较低磁场(0.02 T)下,在12 K附近诱导出铁磁态,因此在一定磁化强度范围内存在AFMΙ-FM,FM-AFMП和AFMП-PM相变。当磁场为0.2 T时AFMΠ态完全消失,AFM-PM的转变成为FM-PM的转变。低温AFMΙ态随磁场的变化是不可逆的,而AFMΠ态随磁场的变化是可逆的。根据温度和磁场的变化绘制了TmGa的磁相图。TmGa在相变温度附近具有较大的磁熵变(-ΔSM),当磁场变化为5 T时,最大-ΔSM为34.2J·kg-1·K-1。值得注意的是,在磁场变化为1和2 T时,最大-ΔSM分别为12.9和20.7 J·kg-1·K-1。同时通过计算得到在1,2和5 T下的磁制冷能力(RC)分别为69,149和364 J·kg-1。TmGa化合物作为低温磁制冷材料潜在巨大应用前景。TmGa alloy was prepared by arc melting. TmGa exhibited two successive magnetic transitions at temperatures,TAF= 11. 5K antiferromagnetic（AFMΙ） to AFMΠand TN= 15 K AFMΠto paramagnetic（PM）. A field-induced metamagnetic transition AFM-FM states was observed. Although the ground state remained AFM for TmGa,the ferromagnetic（FM） state could be induced by a magnetic field at about 12 K under relatively low field change of 0. 02 T. So the transitions AFMΙ-FM,FM-AFMПand AFMП-PM were observed in a certain magnetic field,and the AFMΠstate completely disappeared under 0. 2 T. The transition from low temperature AFM state（AFMI） to FM state induced by a magnetic field was irreversible. On the contrary,the transition from high temperature AFM state（AFMII） to FM state was reversible. A magnetic phase diagram was made based on the magnetic measurement. Additionally,TmGa compound exhibited an excellent magnetocaloric effect（MCE） around transition temperature. Under field change of 5 T,the maximum values of magnetic entropy change-ΔSMwas 34. 2 J·kg^-1·K^-1. It was worth noting that under field changes of 1 and 2 T,the maximum values of-ΔSMwere 12. 9 and 20. 7 J·kg^-1·K^-1,meanwhile,large values of refrigerant capacity（RC）（69,149 and 364J·kg^-1） were observed,respectively. It was expected to have effective applications in low temperature magnetic refrigeration.

关 键 词：磁性材料 相转变 磁相图 磁热效应 

分 类 号：O469[理学—凝聚态物理]