Effect of vacancy defects on geometrically frustrated magnets
Effect of vacancy defects on geometrically frustrated magnets
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DOI：
10.1103/physrevb.106.l140202
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发表时间：
2022-03
影响因子：
3.7
通讯作者：
S. Syzranov
中科院分区：
文献类型：
--
作者：
S. Syzranov
淬灭无序可能会阻止广泛寻求的量子自旋液态（QSL）的形成，或者通过诱导自旋玻璃态来掩盖它们的特征，这就是为什么相当多的实验努力都是针对纯化可能拥有QSL的材料。然而，在几何阻挫（GF）磁体，最大的一类材料中，QSL的寻求，玻璃化转变温度$T_g$的增长与空位缺陷的密度降低，伴随着同时增长的磁化率。在本文中，我们发展了一个唯象理论的玻璃化转变和磁化率在三维几何挫折（GF）磁性材料。我们考虑一个GF磁体模型，其中玻璃化转变发生在没有空位的情况下，例如，由于其他类型的猝灭无序。我们表明，无序，创造弱的局部扰动，例如弱随机应变，导致的增长的转变温度$T_g$。相比之下，空位减少$T_g$为小的空位浓度。空位存在的另一个后果是产生准自旋，即位于空位附近的有效磁矩，它们与体自旋一起对系统的磁化率做出贡献。我们发现，增加空位密度导致的总磁化率的增加。
Quenched disorder may prevent the formation of the widely sought quantum-spin-liquid states (QSLs) or mask their signatures by inducing a spin-glass state, which is why considerable experimental efforts are directed at purifying materials that may host QSLs. However, in geometrically frustrated (GF) magnets, the largest class of materials in which QSLs are sought, the glass-transition temperature $T_g$ grows with decreasing the density of vacancy defects, accompanied by a simultaneous growth of the magnetic susceptibility. In this paper, we develop a phenomenological theory of glass transitions and magnetic susceptibility in 3D geometrically frustrated (GF) magnetic materials. We consider a model of a GF magnet in which the glass transition occurs in the absence of vacancies, e.g., due to other types of quenched disorder. We show that disorder that creates weak local perturbations, e.g. weak random strain, leads to the growth of the transition temperature $T_g$. By contrast, vacancies reduce $T_g$ for small vacancy concentrations. Another consequence of the presence of vacancies is the creation of quasispins, effective magnetic moments localised near the vacancies, that contribute to the magnetic susceptibility of the system together with the bulk spins. We show that increasing the vacancy density leads to an increase of the total magnetic susceptibility.