Chiral ferromagnetism beyond Lifshitz invariants
Peer reviewed, Journal article
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OriginalversjonPhysical review B (PRB). 2020, 101 161403-?. 10.1103/PhysRevB.101.161403
We consider a contribution w ch to the micromagnetic energy density that is linear with respect to the first spatial derivatives of the local magnetization direction. For a generalized two-dimensional 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 wch beyond Lifshitz invariants emerge as a result of spin rotation symmetry breaking caused by SOC. The 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 ch, allowed by symmetry, for each crystallographic point group.