Tb_(3)NiSi_(2)合金磁相变与磁热性能研究  

Magnetic Phase Transition and Magnetocaloric Effect of TbNiSi Alloy

作　　者：陈湘[1] 倪超[1] 赵明骅[1] Chen Xiang;Ni Chao;Zhao Minghua(College of Physics and Electronic Information Engineering,Neijiang Normal University,Neijiang 641112,China)

机构地区：[1]内江师范学院物理与电子信息工程学院,四川内江641112

出　　处：《稀有金属》2021年第2期169-176,共8页Chinese Journal of Rare Metals

基　　金：四川省科技计划项目(2017JY181)资助。

摘　　要：依据X射线衍射(XRD)与等温磁化曲线和等磁场变温磁化曲线,主要研究了Tb_(3)NiSi_(2)合金相结构与磁性相变和磁热性能。XRD表明,采用800℃保温14天,然后炉冷至室温的热处理方法制备的R3NiSi2(R=Tb,Dy,Ho,Er)合金中,主相均为Gd3NiSi2型正交结构(空间群:Pnma,No.62)相,但杂相R5Si3含量存在差异,其规律是从Er到Tb,含量依次减少,Tb_(3)NiSi_(2)合金样品基本为一个单相,其相应晶格常数分别为a=1.1240(8)nm,b=0.41009(8)nm,c=1.12058(1)nm。等温磁化曲线显示在50~300 K温度范围内,Tb_(3)NiSi_(2)合金仅展现出铁磁-顺磁相变,并没有在130,82,66,53 K等观察到相关文献报道的多重的反常反铁磁态-铁磁态(AFM-FM)相变。0.01 T磁场下的磁化强度对温度求导曲线(d M/d T)和0~2 T磁场下的Arrott图结果证实合金铁磁-顺磁二级磁相变居里温度(Tc)=88 K。居里外斯定理拟合表明合金中Tb^(3+)粒子的有效磁矩为9.90μB(μB为玻尔磁子),同期望值μeff/Tb^(3+)=g(J(J+1))1/2=9.72μB基本一致。在磁热性方面,Tb_(3)NiSi_(2)合金在0~2 T磁场范围内,低场响应性较差,铁磁态分子的有效磁矩远低于顺磁分子有效磁矩,最大磁熵变(-ΔSM_(max))为3.2 J·kg^(-1)·K^(-1);在对应的半高宽温跨(δTFWHM)=35.5K范围内,相对制冷量为113 J·kg^(-1)。In R_(3)NiSi_(2) alloys,all atoms occupy 4C position,which may lead to abundant magnetic phenomena.R3NiSi2 alloys have attracted wide attention of researchers.In this work,the phase formation and crystal structure of R3NiSi2 alloys(R=Tb,Dy,Ho and Er)were investigated using X-ray powder diffraction(XRD),and the magnetic phase transition and magnetocaloric effect(MCE)of Tb_(3)NiSi_(2)alloy were studied based on magnetic susceptibility and magnetization measurements.The room temperature XRD patterns showed that the main phases were Gd_(3)NiSi_(2)-type orthogonal structure phase(space group:Pnma,No.62)in R_(3)NiSi_(2) alloys(R=Tb,Dy,Ho and Er)annealed at 800℃for 14 d and cooled down to room temperature in furnace,but the purity amounts of R5 Si3 phase gradually increased from Tb to Er.At the same time,the Rietveld refinement of the powder XRD pattern showed the crystal parameters a,b and c of R_(3)NiSi_(2) alloys decreased linearly in turn from R=Tb to Er.Because the Tb_(3)NiSi_(2)alloy was almost a single phase with a-1.1240(8)nm,b=0.41009(8)nm and c=1.12058(1)nm.The temperature dependences of DC magnetization of Tb_(3)NiSi_(2)alloy(M-T curve)measured by the zero-field-cooled(ZFC)heating and field-cooled cooling(FC)methods in different magnetic fields showed that there was only a ferromagnetic-paramagnetic transition in the temperature range from 50 to 300 K,and the reported abnormal antiferromagnetic(AFM)-ferromagnetic(FM)phase transitions were observed at 130,82,66 and 53 K,respectively.The derivative curve of magnetiation versus temperature(dM/dT)data in a field of 0.1 T and Arrott plots in a field change of 0-2 T indicated that the magnetic order transition in Tb_(3)NiSi_(2)was a typical second order with Curie temperature(Tc)=88 K.The M-T curve of ZFC measurement mode did not coincide with that of FC measurement mode,especially in 0.01 T magnetic field.This phenomenon was similar to that in TbNi4 Si alloy,and the main source was the competition between AFM and FM in the ground state alloy when the temperature

关 键 词：Tb3NiSi2合金 磁相变 磁热效应 

分 类 号：TG132.2[一般工业技术—材料科学与工程]