Electric-field driven stability control of skyrmions in an ultrathin transition-metal film

Abstract

To realize future spintronic applications with magnetic skyrmions—topologically nontrivial swirling spin structures—it is essential to achieve efficient writing and deleting capabilities of these quasi-particles. Electric-field assisted nucleation and annihilation is a promising route, however, the understanding of the underlying microscopic mechanisms is still limited. Here, we show how the stability of individual magnetic skyrmions in an ultrathin transition-metal film can be controlled via external electric fields. We demonstrate based on density functional theory that it is important to consider the changes of all interactions with electric field, i.e., the pair-wise exchange, the Dzyaloshinskii–Moriya interaction, the magnetocrystalline anisotropy energy, and the higher-order exchange interactions. The energy barriers for electric-field assisted skyrmion writing and deleting obtained via atomistic spin simulations vary by up to a factor of three more than the variations of the interactions calculated from first-principles. This surprising effect originates from the electric-field dependent size of metastable skyrmions at a fixed magnetic field. The large changes in lifetimes allow the possibility of electric-field assisted thermally activated writing and deleting of skyrmions.

Atomistic spin simulations of electric-field-assisted nucleation and annihilation of magnetic skyrmions in Pd/Fe/Ir(111)

“…The variation of the different magnetic interactions due to the applied electric field can be explained based on the spin-dependent screening charge in the film as discussed in detail in Refs. [36,40]. Note, that electric-field effects on the exchange interaction which are even by a factor of about two larger than in Pd/Fe/Ir(111) have been reported based on DFT studies for film systems with a Co [36] or an Fe [40] monolayer directly at the surface.…”

“…[36,40]. Note, that electric-field effects on the exchange interaction which are even by a factor of about two larger than in Pd/Fe/Ir(111) have been reported based on DFT studies for film systems with a Co [36] or an Fe [40] monolayer directly at the surface. The induced change in the exchange constant J 1 amounts to ∆J 1 = ±0.29 meV for an electric field of E = ±0.5 V/ Å (cf.…”

“…As mentioned in the introduction, the application of an electric field leads to a spin-dependent screening by the electron density at the surface which changes the magnetic interactions. Motivated by results from DFT [34,36,37,40,47] we model the influence of the electric field in linear response to the magnetic interactions.…”

“…Ref. [40]), only the Pd/Fe interface is much affected. The hybridization at this interface has a strong effect on I.…”

“…Applying an electric field perpendicular to the surface of a metallic film will act on the magnetic interactions due to the magnetoelectric-and Rashba effect [34][35][36][37][38][39][40]. As a result the energy and entropy of states will be influenced, making either nucleation or annihilation processes more likely to occur.…”