Reciprocal space mapping of magnetic order in thick epitaxial MnSi films

TL;DR

This study uses neutron scattering and reflectometry to map magnetic order in thick epitaxial MnSi films, revealing a simple magnetic modulation without skyrmions, contrasting with bulk behavior, influenced by Si position shifts.

Contribution

It provides the first reciprocal space mapping of magnetic order in thick epitaxial MnSi films, showing the absence of skyrmions and highlighting the role of Si atomic positions.

Findings

Magnetic modulation is perpendicular to the film under various fields.

No evidence of skyrmion formation in the epitaxial films.

Si position shifts influence the magnetic state.

Abstract

We report grazing incidence small angle neutron scattering (GISANS) and complementary off-specular neutron reflectometry (OSR) of the magnetic order in a single-crystalline epitaxial MnSi film on Si(111) in the thick film limit. Providing a means of direct reciprocal space mapping, GISANS and OSR reveal a magnetic modulation perpendicular to the films under magnetic fields parallel and perpendicular to the film, where additional polarized neutron reflectometry (PNR) and magnetization measurements are in excellent agreement with the literature. Regardless of field orientation, our data does not suggest the presence of more complex spin textures, notably the formation of skyrmions. This observation establishes a distinct difference with bulk samples of MnSi of similar thickness under perpendicular field, in which a skyrmion lattice dominates the phase diagram. Extended x-ray absorption fine structure measurements suggest that small shifts of the Si positions within the unstrained unit cell control the magnetic state, representing the main difference between the films and thin bulk samples.