Kostiantyn Yershov – RiTM

Curvature effects on phase transitions in chiral magnets

Kostiantyn Yershov — Fri, 02 Oct 2020 08:25:52 +0000

Periodical equilibrium states of magnetization exist in chiral ferromagnetic films, if the constant of antisymmetric exchange (Dzyaloshinskii-Moriya interaction) exceeds some critical value. Here, we demonstrate that this critical value can be significantly modified in curved film. The competition between symmetric and antisymmetric exchange interactions in a curved film can lead to a new type of domain wall which is inclined with respect to the cylinder axis. The wall structure is intermediate between Bloch and Néel ones. The exact analytical solutions for phase boundary curves and the new domain wall are obtained.

Publication:

Kostiantyn Yershov, Volodymyr Kravchuk, Denis Sheka, and Ulrich Rößler,
Curvature effects on phase transitions in chiral magnets,
SciPost Phys.9, 043(2020), doi:10.21468/SciPostPhys.9.4.043 pdf

Geometry-induced motion of magnetic domain walls in curved nanostripes

Kostiantyn Yershov — Sun, 23 Sep 2018 12:46:44 +0000

Dynamics of topological magnetic textures are typically induced externally by, e.g., magnetic fields or spin/charge currents. Here, we demonstrate the effect of the internal-to-the-system geometry-induced motion of a domain wall in a curved nanostripe. Being driven by a gradient of the curvature of a stripe with biaxial anisotropy, transversal domain walls acquire remarkably high velocities of up to 100 m/s and do not exhibit any Walker-type speed limit. We pinpoint that the inhomogeneous distribution of the curvature-induced Dzyaloshinskii-Moriya interaction is a driving force for the motion of a domain wall. Although we showcase our approach on the specific Euler spiral geometry, the approach is general and can be applied to a wide class of geometries.
Phys. Rev. B 98, 060409(R) (2018), PDF

Curvature and torsion effects in spin-current driven domain wall motion

Kostiantyn Yershov — Tue, 15 Mar 2016 18:24:05 +0000

The domain wall motion along a helix-shaped nanowire is studied for the case of spin-current driving via the Zhang-Li mechanism. The analysis is based on the collective variable approach. Two effects are ascertained: (i) the curvature results in the appearance of the Walker limit for a uniaxial wire, and (ii) the torsion results in effective shift of the nonadiabatic spin torque parameter β. The latter effect changes considerably the domain wall velocity and can result in negative domain wall mobility. This effect can be also used for an experimental determination of the nonadiabatic parameter β and damping coefficient α.

Phys. Rev. B. 92, 094418 (2016), PDF