Macroscopic evidence of skyrmion lattice inhomogeneity and magnetic vortex states in the A-phase of MnSi

TL;DR

This study provides the first macroscopic evidence of inhomogeneity and vortex-like states within the A-phase of MnSi, revealing distinct skyrmion lattice behaviors through magnetoresistance anisotropy measurements.

Contribution

It introduces a novel experimental approach to identify skyrmion lattice inhomogeneity and vortex states in MnSi using magnetoresistance anisotropy.

Findings

A-phase core exhibits isotropic magnetoresistance indicating uniform skyrmion density.

Anisotropic MR observed at the A-phase border and other phases, linked to magnetic scattering.

Evidence suggests two types of skyrmion lattices exist within the A-phase, including vortex-like states.

Abstract

The magnetic inhomogeneity of the A-phase in MnSi chiral magnet is identified for the first time from the precise measurements of transverse magnetoresistance (MR) anisotropy. The area inside the A-phase (A-phase core) corresponds to isotropic MR having no confinement to the MnSi crystal lattice. Per contra, the MR becomes anisotropic both on the border of the A-phase and in other magnetic phases, the strongest magnetic scattering being observed when external magnetic field applied along [001] or [00-1] directions. We argue here that the established MR features prove the presence of two different types of the skyrmion lattices inside the A-phase, and the dense skyrmion state of the A-phase core is built from individual skyrmions similar to Abrikosov-type magnetic vortexes.