Observation of short-period helical spin order and magnetic transition in a non-chiral centrosymmetric helimagnet

TL;DR

This study reports the real-space observation of nanoscale helical spin order in a non-chiral centrosymmetric helimagnet at room temperature, revealing a magnetic transition to cycloidal order below 228 K, with implications for emergent electromagnetism.

Contribution

First direct real-space observation of nanoscale helical spin order in a non-chiral centrosymmetric material at room temperature, linking magnetic transition to magneto-crystalline anisotropy.

Findings

Nanoscale helical spin order with a 3.2 nm period observed at room temperature.

Magnetic transition from helical to cycloidal order below 228 K.

Temperature-induced variation in magneto-crystalline anisotropy drives the transition.

Abstract

The search for materials exhibiting nanoscale spiral order continues to be fuelled by the promise of emergent inductors. Although such spin textures have been reported in many materials, most of them exhibit long periods or are limited to operate far below room temperature. Here, we present the real-space observation of an ordered helical spin order with a period of 3.2 nm in a non-chiral centrosymmetric helimagnet MnCoSi at room temperature via multi-angle and multi-azimuth approach of Lorentz transmission electron microscopy (TEM). A magnetic transition from the ordered helical spin order to a cycloidal spin order below 228 K is clearly revealed by in situ neutron powder diffraction and Lorentz TEM, which is closely correlated with temperature-induced variation in magneto-crystalline anisotropy. These results reveal the origin of spiral ordered spin textures in non-chiral centrosymmetric helimagnet, which can serve as a new strategy for searching materials with nanoscale spin order with potential applications in emergent electromagnetism.