New spiral state and skyrmion lattice in 3D model of chiral magnets

TL;DR

This paper reveals a new surface magnetic state and details the phase diagram of 3D chiral magnets, showing how surface states and skyrmion lattices depend on film thickness and magnetic field, with implications for experiments and applications.

Contribution

It introduces a novel 3D surface magnetic state in chiral magnets and maps the conditions for skyrmion lattice stability, advancing understanding of magnetic phases in thin films.

Findings

Discovery of a surface chiral spin-texture state

Identification of conditions for skyrmion lattice ground state

Phase diagram mapping for various film thicknesses and magnetic fields

Abstract

We present the phase diagram of magnetic states for films of isotropic chiral magnets calculated as function of applied magnetic field and thickness of the film. We have found a novel magnetic state driven by the natural confinement of the crystal, localized at the surface and stacked on top of the conical bulk phase. This magnetic surface state has a three-dimensional (3D) chiral spin-texture described by the superposition of helical and cycloidal spin spirals. This surface state exists for a large range of applied magnetic fields and for any film thickness beyond a critical one. We also identified the whole thickness and field range for which the skyrmion lattice becomes the ground state of the system. Below a certain critical thickness the surface state and bulk conical phase are suppressed in favor of the skyrmion lattice. Unraveling of those phases and the construction of the phase diagram became possible using advanced computational techniques for direct energy minimization applied to a basic 3D model for chiral magnets. Presented results provide a comprehensive theoretical description for those effects already observed in experiments on thin films of chiral magnets, predict new effects important for applications and open perspectives for experimental studies of such systems.