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arXiv · 1904.05337

Chiral ferromagnetism beyond Lifshitz invariants

I. A. Ado·A. Qaiumzadeh·A. Brataas·M. Titov
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Abstract

We consider a contribution $w_{\text{ch}}$ to the micromagnetic energy density that is linear with respect to the first spatial derivatives of the local magnetization direction. For a generalized 2D Rashba ferromagnet, we present a microscopic analysis of this contribution and, in particular, demonstrate that it cannot be expressed through Lifshitz invariants beyond the linear order in the spin-orbit coupling (SOC) strength. Terms in $w_{\text{ch}}$ beyond Lifshitz invariants emerge as a result of spin rotation symmetry breaking caused by SOC. Effects of these terms on the phase diagram of magnetic states and spin-wave dispersion are discussed. Finally, we present a classification of terms in $w_{\text{ch}}$, allowed by symmetry, for each crystallographic point group.

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I. A. Ado, A. Qaiumzadeh, A. Brataas, M. Titov. 2019-04-10. Chiral ferromagnetism beyond Lifshitz invariants. https://doi.org/10.1103/physrevb.101.161403

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