Wu Mengxin, Han Yilin, Bouhemadou A, Cheng Zhenxiang, Khenata R, Kuang Minquan, Wang Xiangjian, Yang Tie, Yuan Hongkuan, Wang Xiaotian
School of Physical Science and Technology, Southwest University, Chongqing 400715, People's Republic of China.
Laboratory for Developing New Materials and Their Characterization, University Ferhat Abbas Setif 1, Setif 19000, Algeria.
IUCrJ. 2019 Jan 24;6(Pt 2):218-225. doi: 10.1107/S2052252518017578. eCollection 2019 Mar 1.
In this work, two kinds of competition between different Heusler structure types are considered, one is the competition between XA and L2 structures based on the cubic system of full-Heusler alloys, Pd ( = Co, Fe, Mn; = B, Al, Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Sb). Most alloys prefer the L2 structure; that is, Pd atoms tend to occupy the (0, 0, 0) and (0.5, 0.5, 0.5) Wyckoff sites, the atom is generally located at site (0.25, 0.25, 0.25), and the main group element has a preference for site (0.75, 0.75, 0.75), meeting the well known site-preference rule. The difference between these two cubic structures in terms of their magnetic and electronic properties is illustrated further by their phonon dispersion and density-of-states curves. The second type of competition that was subjected to systematic study was the competitive mechanism between the L2 cubic system and its L1 tetragonal system. A series of potential tetragonal distortions in cubic full-Heusler alloys (Pd ) have been predicted in this work. The valley-and-peak structure at, or in the vicinity of, the Fermi level in both spin channels is mainly attributed to the tetragonal ground states according to the density-of-states analysis. Δ is defined as the difference between the most stable energy values of the cubic and tetragonal states; the larger the value, the easier the occurrence of tetragonal distortion, and the corresponding tetragonal structure is stable. Compared with the Δ values of classic Mn-based tetragonal Heusler alloys, the Δ values of most PdCo alloys in this study indicate that they can overcome the energy barriers between cubic and tetragonal states, and possess possible tetragonal transformations. The uniform strain has also been taken into consideration to further investigate the tetragonal distortion of these alloys in detail. This work aims to provide guidance for researchers to further explore and study new magnetic functional tetragonal materials among the full-Heusler alloys.
在本研究中，考虑了不同赫斯勒结构类型之间的两种竞争，一种是基于全赫斯勒合金立方体系的XA和L2结构之间的竞争，其中Pd（=Co、Fe、Mn；=B、Al、Ga、In、Tl、Si、Ge、Sn、Pb、P、As、Sb）。大多数合金倾向于L2结构；也就是说，Pd原子倾向于占据（0,0,0）和（0.5,0.5,0.5）的Wyckoff位置，原子通常位于（0.25,0.25,0.25）位置，主族元素倾向于占据（0.75,0.75,0.75）位置，符合著名的位置偏好规则。这两种立方结构在磁学和电学性质方面的差异通过它们的声子色散和态密度曲线进一步说明。进行系统研究的第二种竞争类型是L2立方体系与其L1四方体系之间的竞争机制。本研究预测了立方全赫斯勒合金（Pd）中一系列潜在的四方畸变。根据态密度分析，两个自旋通道中费米能级处或其附近的谷峰结构主要归因于四方基态。Δ定义为立方态和四方态最稳定能量值之间的差值；该值越大，四方畸变越容易发生，相应的四方结构越稳定。与经典的锰基四方赫斯勒合金的Δ值相比，本研究中大多数PdCo合金的Δ值表明它们可以克服立方态和四方态之间的能垒，并具有可能的四方转变。还考虑了均匀应变以进一步详细研究这些合金的四方畸变。这项工作旨在为研究人员在全赫斯勒合金中进一步探索和研究新型磁性功能四方材料提供指导。
