The magnets are typically classified into Stoner and Heisenberg type, depending on the itinerant or localized nature of the constituent magnetic moments. In this work, we investigate theoretically the behaviour of the magnetic moments of iron and cobalt in their B2-ordered alloy. The results based on local spin density approximation for the density functional theory (DFT) suggest that the Co magnetic moment strongly depends on the directions of the surrounding magnetic moments, which usually indicates the Stoner-type mechanism of magnetism. This is consistent with the disordered local moment picture of the paramagnetic state, where the magnetic moment of cobalt gets substantially suppressed. We argue that this is due to the lack of strong on-site electron correlations, which we take into account by employing a combination of DFT and dynamical mean-field theory (DMFT). Within LDA + DMFT, we find a substantial quasiparticle mass renormalization and a non Fermi-liquid behaviour of Fe–3d orbitals. The resulting spectral functions are in very good agreement with measured spin-resolved photoemission spectra. Our results suggest that local correlations play an essential role in stabilizing a robust local moment on Co in the absence of magnetic order at high temperatures.

根据组成磁矩的流动或局部性质，磁体通常分为斯通纳和海森堡类型。在这项工作中，我们从理论上研究了铁和钴在 B2 有序合金中的磁矩行为。基于密度泛函理论（DFT）的局部自旋密度近似的结果表明，Co磁矩强烈依赖于周围磁矩的方向，这通常表明磁性的斯托纳型机制。这与顺磁状态的无序局部矩图一致，其中钴的磁矩被大大抑制。我们认为这是由于缺乏强烈的现场电子相关性，我们通过结合 DFT 和动态平均场理论 (DMFT) 来考虑这一点。在 LDA + DMFT 中，我们发现了一个实质性的准粒子质量重整化和 Fe-3 的非费米液体行为d轨道。得到的光谱函数与测量的自旋分辨光电子光谱非常一致。我们的结果表明，在高温下没有磁序的情况下，局部相关性在稳定 Co 上的稳健局部矩方面起着至关重要的作用。