FeGe in the B20 phase is an experimentally well-studied prototypical chiral magnet exhibiting helical spirals, skyrmion lattices, and individual skyrmions with a robust length of 70 nm. While the helical spiral ground state can be verified by first-principles calculations based on density functional theory, this feature size could not be reproduced even approximately. To develop a coherent picture of the discrepancy between experiment and theory, we investigate in this work the magnetic properties of FeGe from first principles using different electronic-structure methods. We study atomistic as well as micromagnetic parameters describing exchange and Dzyaloshinskii-Moriya interactions, and discuss their subtle dependence on computational, structural, and correlation parameters. In particular, we quantify how these magnetic properties are affected by changes of the lattice parameter, different atomic arrangements, exchange and correlation effects, finite Fermi-function broadening, and momentum-space sampling. In addition, we use the obtained atomistic parameters to determine the corresponding Curie temperature, which agrees well with experiments. Our results indicate that the well-known and well-accepted relation between the micromagnetic parameters and the period of the helical structure is not valid for FeGe. This calls for new experiments exploring the relation by measuring independently the spin stiffness, the spiralization, and the period of the helical spin spiral.

中文翻译：

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原型B20手性磁体FeGe的磁性能从头算分析

B20相中的FeGe是一种经过实验研究的原型手性磁体，具有螺旋螺旋形，天sky子晶格和坚固的70纳米长的单个天rm子。虽然可以通过基于密度泛函理论的第一性原理计算来验证螺旋形螺旋基态，但该特征尺寸甚至无法近似再现。为了弄清楚实验与理论之间的差异，我们在这项工作中使用不同的电子结构方法从第一性原理研究了FeGe的磁性能。我们研究描述交换和Dzyaloshinskii-Moriya相互作用的原子和微磁参数，并讨论它们对计算，结构和相关参数的微妙依赖。特别是，我们量化了晶格参数，不同原子排列，交换和相关效应，有限费米函数加宽以及动量空间采样对磁特性的影响。另外，我们使用获得的原子参数来确定相应的居里温度，这与实验吻合得很好。我们的结果表明，微磁参数和螺旋结构的周期之间的公知和公认的关系对于FeGe无效。这要求通过独立测量自旋刚度，螺旋度和螺旋自旋螺旋的周期来探索这种关系的新实验。另外，我们使用获得的原子参数来确定相应的居里温度，这与实验吻合得很好。我们的结果表明，微磁参数和螺旋结构的周期之间的公知和公认的关系对于FeGe无效。这要求通过独立测量自旋刚度，螺旋度和螺旋自旋螺旋的周期来探索这种关系的新实验。另外，我们使用获得的原子参数来确定相应的居里温度，这与实验吻合得很好。我们的结果表明，微磁参数和螺旋结构的周期之间的公知和公认的关系对于FeGe无效。这要求通过独立测量自旋刚度，螺旋度和螺旋自旋螺旋的周期来探索这种关系的新实验。