Ab initio analysis of magnetic properties of prototype B20 chiral magnet FeGe

Abstract

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.

13 pages, 8 figures

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• Giant generic topological Hall resistivity of MnSi under pressure
• First-principles prediction of high Curie temperature for ferromagnetic bcc-Co and bcc-FeCo alloys and its relevance to tunneling magnetoresistance
• First-Principles Evaluation of the Dzyaloshinskii--Moriya Interaction
• Hidden quantum phase transition in Mn${}_{1-x}$Fe${}_x$Ge: evidence brought by small-angle neutron scattering
• Higher-dimensional Wannier interpolation for the modern theory of the Dzyaloshinskii-Moriya interaction: Application to Co-based trilayers
• Composition-dependent magnetic response properties of Mn${}_{1-x}$Fe${}_x$Ge alloys
• Higher dimensional Wannier functions of multi-parameter Hamiltonians

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• Micromagnetic description of twisted spin spirals in the B20 chiral magnet FeGe from first principles
• Electronic and dynamical properties of cobalt monogermanide CoGe phases under pressure
• Tuning magnetic exchange interactions in 2D magnets: the case of CrGeX${}_3$ (X = Se, Te) and Janus Cr${}_2$Ge${}_2$(Se,Te)${}_3$ monolayers
• Experimental determination of the spin Hamiltonian of the cubic chiral magnet MnSi
• Magnetoelectricity of Topological Solitons in 2D Magnets
• The influence of antiferromagnetic spin cantings on the magnetic helix pitch in cubic helimagnets
• Helical spin dynamics in Cu${}_2$OSeO${}_3$ as measured with small-angle neutron scattering
• Origin of the suppression of magnetic order in MnSi under hydrostatic pressure
• Non-collinear magnetism contra frustration: Magnetic order and anisotropy in hexagonal MnPtGa
• General spin models from noncollinear spin density functional theory and spin-cluster expansion