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arXiv 2202.02792cond-mat.mtrl-scicond-mat.str-el
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固态磁性团簇顺磁磁化率的半经验分析

A semi-empirical analysis of the paramagnetic susceptibility of solid state magnetic clusters

Lauro B. Braz, Fernando A. Garcia

摘要:

新的磁性材料合成的最新进展导致了新的量子顺磁体的发现。这些材料中的许多,例如钙钛矿Ba $_{4}$ LnMn $_{4}$ O $_{12}$(Ln = Sc或Nb)、Ba $_{3}$ Mn $_{2}$ O $_{8}$和Sr $_{3}$ Cr $_{2}$ O $_{8}$,呈现具有强的簇内相互作用但弱的簇间相互作用的孤立的磁性簇,这延迟了有序到较低温度($T$)的开始。这种局部能量尺度和磁有序温度之间的偏移是磁阻挫的标志。在足够高的$T$下,阻挫团簇磁体的顺磁磁化率($χ$)可以符合居里-外斯定律,但所得的微观参数一般不能与其他方法得到的参数相一致。在这项工作中,我们提出了一个分析微观理论,以获得$χ$的二聚体和三聚体集群磁铁,两个最常见的文献中,利用合适的海森堡型哈密顿。我们还加入了平均场水平上的团簇间相互作用,从而得到了系统临界温度的表达式,并定义了一个新的有效阻挫参数$f_{\text{eff}}$。我们的方法是通过处理一些选定的材料的$χ$数据的例子。

英文摘要:

Recent developments in the synthesis of new magnetic materials lead to the discovery of new quantum paramagnets. Many of these materials, such as the perovskites Ba$_{4}$LnMn$_{4}$O$_{12}$ (Ln = Sc or Nb), Ba$_{3}$Mn$_{2}$O$_{8}$, and Sr$_{3}$Cr$_{2}$O$_{8}$ present isolated magnetic clusters with strong intracluster interactions but weak intercluster interactions, which delays the onset of order to lower temperatures ($T$). This offset between the local energy scale and the magnetic ordering temperature is the hallmark of magnetic frustration. At sufficient high-$T$, the paramagnetic susceptibility ($χ$) of frustrated cluster magnets can be fit to a Curie-Weiss law, but the derived microscopic parameters cannot in general be reconciled with those obtained from other methods. In this work, we present an analytical microscopic theory to obtain $χ$ of dimer and trimer cluster magnets, the two most commonly found in literature, making use of suitable Heisenberg-type Hamiltonians. We also add intercluster interactions in a mean-field level, thus obtaining an expression to the critical temperature of the system and defining a new effective frustration parameter $f_{\text{eff}}$. Our method is exemplified by treating the $χ$ data of some selected materials.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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