Metamagnetic transition and magnetocaloric properties in antiferromagnetic Ho2Ni2Ga and Tm2Ni2Ga compounds
Metamagnetic transition and magnetocaloric properties in antiferromagnetic Ho2Ni2Ga and Tm2Ni2Ga compounds
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反铁磁 Ho2Ni2Ga 和 Tm2Ni2Ga 化合物的变磁转变和磁热特性
DOI：
10.1016/j.intermet.2017.12.013
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发表时间：
2018-03-01
期刊：
影响因子：
4.4
通讯作者：
Wilde, Gerhard
中科院分区：
文献类型：
--
作者：
Zhang, Yikun;Yang, Yang;Wilde, Gerhard
利用X射线衍射仪、扫描电子显微镜、能谱和磁化强度测量等手段，系统地研究了三元金属间化合物Ho2Ni2Ga和Tm2Ni2Ga的结构、磁相变和磁热性质。粉末X射线衍射和Rietveld细化表明，Ho2Ni2Ga和Tm2Ni2Ga结晶为属于Inunm空间群的W2B2Co型正交结构。这两种化合物在低温和低磁场下都是反铁磁性有序的，并伴随着场诱导的从反铁磁(AFM)到铁磁(FM)的亚磁转变。这两个化合物都观察到了独特而相似的磁热性质，即在低磁场变化(AM和低温)下的逆磁热效应(正磁熵变化，Delta S-M)以及在高Delta H下的大的法向可逆磁热效应。Neel温度(T-N)下/在Neel温度(T-N)下的正Delta S-M归因于从反铁磁(AFM)到铁磁(FM)的一级跃迁，而TN以上的负Delta S-M是由于顺磁(PM)到铁磁(FM)态的磁转变。根据随磁场变化的磁化强度数据，建立了Ho2Ni2Ga的最大磁熵变(-Delta S-M(Max))、相对致冷力(Rcp)和致冷量(Rc)，分别为9.6J/kgK、276J/kg和206J/kg；磁场变化为0-70kOe时，Tm2Ni2Ga分别为4.3J/kgK、60J/kg和46J/kg。
The structure, magnetic transition and magnetocaloric properties in the ternary gallium intermetallic compounds of Ho2Ni2Ga and Tm2Ni2Ga have been systematically investigated by using X-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and magnetization measurements. As found from powder XRD and Rietveld refinement, Ho2Ni2Ga and Tm2Ni2Ga crystallized in an orthorhombic structure of the W2B2Co type belonging to the Inunm space group. Both compounds are ordering anti-ferromagnetically at low temperatures and under low magnetic fields together with a field-induced metamagnetic transition from antiferromagnetic (AFM) to ferromagnetic (FM). Peculiar and similar magnetocaloric properties are observed for both compounds, i.e., an inverse magnetocaloric effect (positive magnetic entropy change, Delta S-M) under low magnetic field changes (AM and at low temperatures together with a large normal reversible magnetocaloric effect under high Delta H. The positive Delta S-M below/at the Neel temperatures (T-N) is ascribed to first order transition from antiferromagnetic (AFM) to ferromagnetic (FM) states, whereas the negative Delta S-M above TN is due to the fact of the magnetic transition from paramagnetic (PM) to ferromagnetic (FM) states. Based on the field-dependent magnetization data, the maximum magnetic entropy change (-Delta S-M(max)), relative cooling power (RCP) and refrigerant capacity (RC) are established, and the corresponding values are 9.6 J/kg K, 276 J/kg and 206 J/kg for Ho2Ni2Ga, and are 4.3 J/kg K, 60 J/kg and 46 J/kg for Tm2Ni2Ga, respectively, for a magnetic field change of 0-70 kOe.