Gao Penglin, Xia Yuanhua, Gong Jian, Ju Xin
School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China.
Key Laboratory of Neutron Physics and Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China.
Nanomaterials (Basel). 2022 May 7;12(9):1586. doi: 10.3390/nano12091586.
The magnetic interactions of iron-rich manganese-based ThMn12 type rare earth metal intermetallic compounds are extremely complex. The antiferromagnetic structure sublattice and the ferromagnetic structure sublattice had coexisted and competed with each other. Previous works are focus on studying magnetic properties of RFexMn12−x (x = 0−9.0, Δx = 0.2). In this work, we obtained a detailed magnetic phase diagram for iron-rich ErFexMn12−x series alloy samples with a fine composition increment (Δx = 0.2), and studied the exchange bias effect and magneto-caloric effect of samples. ErFexMn12−x series (x = 7.0−9.0, Δx = 0.2) alloy samples were synthesized by arc melting, and the pure ThMn12-type phase structure was confirmed by X-ray diffraction (XRD). The neutron diffraction test was used to confirm the Mn atom preferentially occupying the 8i position and to quantify the Mn. The magnetic properties of the materials were characterized by a comprehensive physical property measurement system (PPMS). Accurate magnetic phase diagrams of the samples in the composition range 7.0−9.0 were obtained. Along with temperature decrease, the samples experienced paramagnetic, ferromagnetic changes for samples with x < 7.4 and x > 8.4, and paramagnetic, antiferromagnetic and ferromagnetic or paramagnetic, ferromagnetic and antiferromagnetic changes for samples with 7.4 ≤ x ≤ 8.2. The tunable exchange bias effect was observed for sample with 7.4 ≤ x ≤ 8.2, which resulting from competing magnetic interacting among ferromagnetic and antiferromagnetic sublattices. The maximum magnetic entropy change in an ErFe9.0Mn3.0 specimen reached 1.92 J/kg/K around room temperature when the magnetic field change was 5 T. This study increases our understanding of exchange bias effects and allows us to better control them.
富含铁的锰基ThMn12型稀土金属间化合物的磁相互作用极其复杂。反铁磁结构亚晶格和铁磁结构亚晶格共存并相互竞争。先前的工作主要集中在研究RFexMn12−x（x = 0−9.0，Δx = 0.2）的磁性能。在这项工作中，我们获得了具有精细成分增量（Δx = 0.2）的富含铁的ErFexMn12−x系列合金样品的详细磁相图，并研究了样品的交换偏置效应和磁热效应。通过电弧熔炼合成了ErFexMn12−x系列（x = 7.0−9.0，Δx = 0.2）合金样品，并通过X射线衍射（XRD）确认了纯ThMn12型相结构。利用中子衍射测试来确认Mn原子优先占据8i位置并对Mn进行定量。通过综合物性测量系统（PPMS）对材料的磁性能进行了表征。获得了成分范围为7.0−9.0的样品的精确磁相图。随着温度降低，对于x < 7.4和x > 8.4的样品，经历了顺磁、铁磁变化；对于7.4 ≤ x ≤ 8.2的样品，经历了顺磁、反铁磁和铁磁或顺磁、铁磁和反铁磁变化。在7.4 ≤ x ≤ 8.2的样品中观察到了可调谐的交换偏置效应，这是由铁磁和反铁磁子晶格之间的竞争磁相互作用引起的。当磁场变化为5 T时，ErFe9.0Mn3.0样品在室温附近的最大磁熵变达到1.92 J/kg/K。这项研究增进了我们对交换偏置效应的理解，并使我们能够更好地控制它们。
