RPdAl(R=Gd-Er)的磁性和磁热效应  

Magnetic Properties and Magnetocaloric Effects in RPdAl(R=Gd-Er)

作　　者：许志一[1] 沈俊[2] 沈保根[1] 

机构地区：[1]中国科学院物理研究所磁学国家重点实验室,北京100190 [2]中国科学院理化技术研究所低温重点实验室,北京100190

出　　处：《中国材料进展》2013年第2期84-93,101,共11页Materials China

基　　金：国家自然科学基金项目(11274357;11004204;51021061;51271192);国家科技部863项目(2011AA03A404);中国科学院重要方向性项目资助

摘　　要：低温退火的LTM-RPdAl和高温退火的HTM-RPdAl分别具有正交TiNiSi型和六角ZrNiAl型结构。综述了磁场和温度变化对LTM-RPdAl和HTM-RPdAl化合物磁性和磁热效应的影响。实验结果表明,LTM-RPdAl化合物均是反铁磁性的,当R=Gd,Tb,Dy,Ho,Er时,奈尔温度TN分别为31,45,21,10和10 K。对于HTM-RPdAl化合物,当R=Tb,Ho,Er时是反铁磁性的,TN分别为43,12和5 K,而当R=Gd,Dy时是铁磁性的,其居里温度分别为TC=49,25 K。反铁磁RPdAl化合物均呈现磁场诱导的反铁磁-铁磁变磁转变。对HTM-RPdAl(R=Ho,Er)化合物,由于弱的反铁磁耦合,在低磁场下呈现出高的饱和磁化强度,从而产生大的磁热效应,在0～5 T磁场变化下的最大磁熵变值和制冷能力分别高达20.6,24.3 J/kg.K和386,299 J/kg,是优异的低温磁制冷材料。In this article, the investigation progress is reviewed in magnetic field and temperature dependences of the magnetic properties and magnetocaloric effects （MCEs） for RPdA1 compounds with the orthorhombic TiNiSi-type （LTM） and the hexagonal ZrNiAl-type （HTM） structures. The LTM-RPdAI （R = Gd, Tb, Dy, Ho and Er） compounds are found to be antiferromagnet with the N^el temperature TN =31,45, 21, 10 and l0 K, respectively. It has been confirmed that the HTM-RPdAI （R = Tb, Ho and Er） compounds undergo the antiferromagnetic （AFM） -to-paramagnetic （PM） transi- tion at TN = 43, 12 and 5 K, while the HTM-RPdA1 （R = Gd and Dy） compounds undergo the ferromagnetic （FM）-to-PM transition at their respective Curie temperature, which is Tc = 49 K and 25 K, respectively. A field-induced metamagnetic transition from AFM to FM state is observed below TN in the antiferromagnetic RPdA1. For the HTM-RPdA1 （ R = Ho and Er） compounds, a small magnetic field can induce an FM-like state due to a weak AFM coupling, which leads to a high saturation magnetization, and gives rise to a large MCE around TN. The maximum value of magnetic entropy change （ ASM ） reaches - 20.6 and - 24.3 J/kg · K with a refrigerant capacity （RC） value of 386 and 299 J/kg around TN for a field change of 0 - 5 T, respectively. The large △SM and considerable RC suggest that HTM-RPdA1 may be an appropriate candidate for magnetic refrigerant in low temperature ranges.

关 键 词：RPdAl化合物 结构 磁性 磁熵变 磁热效应 

分 类 号：O482.6[理学—固体物理]