arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2202.03205cond-mat.str-el
收藏

L1的库仑关联和磁性:DFT + DMFT研究

Coulomb correlations and magnetic properties of L1$_0$ FeCo: a DFT+DMFT study

A. S. Belozerov, A. A. Katanin, V. I. Anisimov

摘要:

我们认为电子相关效应及其对四方畸变化学有序FeCo合金(L1 $_0$结构)的磁性能的影响是一个有前途的无稀土永磁体的候选人。我们采用了一个国家的最先进的方法相结合的密度泛函和动力学平均场理论。根据我们的计算结果,预测的居里温度随着晶格参数比$c/a$的增加而降低,在${c/a=1.22}$处接近850 K。对于所有考虑的$c/a$从1到$\sqrt{2}$,我们发现良好的本地化的磁矩Fe网站,这是由于强相关性起源于洪德的耦合。同时,Co位的磁性更具有流动性,局部磁矩的寿命要短得多。然而,这些短暂的局部时刻也是由于洪德的交换而形成的。在Fe网站的电子态的特征在于由非准粒子形式的自能,而那些为Co网站被发现具有费米液体状的形状与准粒子质量增强因子${m^*/m\sim 1.4}$,对应于适度相关的金属。铁网站上的强电子相关性导致洪德的金属行为可以解释的特殊性的状态密度,它有明显的峰值附近的费米能级,而较弱的多体效应的Co网站可以造成较强的偏离半填充的$3d$状态。磁化率的动量依赖性表明,铁磁有序是最有利的,除了附近的fcc结构和磁交换预计是RKKY型。

英文摘要:

We consider electronic correlation effects and their impact on magnetic properties of tetragonally distorted chemically ordered FeCo alloys (L1$_0$ structure) being a promising candidate for rare-earth-free permanent magnets. We employ a state-of-the-art method combining density functional and dynamical mean-field theory. According to our results, the predicted Curie temperature reduces with increase of lattice parameters ratio $c/a$ and reaches nearly 850 K at ${c/a=1.22}$. For all considered $c/a$ from 1 to $\sqrt{2}$, we find well-localized magnetic moments on Fe sites, which are formed due to strong correlations originating from Hund's coupling. At the same time, magnetism of Co sites is more itinerant with a much less lifetime of local magnetic moments. However, these short-lived local moments are also formed due to Hund's exchange. Electronic states at Fe sites are characterized by a non-quasiparticle form of self-energies, while the ones for Co sites are found to have a Fermi-liquid-like shape with quasiparticle mass enhancement factor ${m^*/m\sim 1.4}$, corresponding to moderately correlated metal. The strong electron correlations on Fe sites leading to Hund's metal behaviour can be explained by peculiarities of the density of states, which has pronounced peaks near the Fermi level, while weaker many-body effects on Co sites can be caused by stronger deviation from half-filling of their $3d$ states. The obtained momentum dependence of magnetic susceptibility suggests that the ferromagnetic ordering is the most favourable one except for the near vicinity of the fcc structure and the magnetic exchange is expected to be of RKKY type.

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。

↑