Hybrid Bloch-N\'eel spiral states in Mn$_{1.4}$PtSn probed by resonant soft x-ray scattering

TL;DR

This study uncovers a novel hybrid spiral magnetic state in Mn$_{1.4}$PtSn, demonstrating its complex, tunable magnetic textures influenced by $D_{2d}$ symmetry, with implications for fundamental physics and energy-efficient technologies.

Contribution

It provides the first experimental evidence of a hybrid Nél and Bloch-type spiral state in Mn$_{1.4}$PtSn using resonant soft x-ray scattering.

Findings

Discovery of a metastable hybrid spin-spiral phase.

Control over spiral orientation and period through external fields.

Evidence of $D_{2d}$ symmetry influence on magnetic textures.

Abstract

Multiple intriguing phenomena have recently been discovered in tetragonal Heusler compounds, where $D_{2d}$ symmetry sets a unique interplay between Dzyaloshinskii-Moriya (DM) and magnetic dipolar interactions. In the prototype $D_{2d}$ compound Mn$_{1.4}$PtSn, this has allowed the stabilization of exotic spin textures such as first-reported anti-skyrmions or elliptic Bloch-type skyrmions. While less attention has so far been given to the low-field spiral state, this remains extremely interesting as a simplest phase scenario on which to investigate the complex hierarchy of magnetic interactions in this materials family. Here, via resonant small-angle soft x-ray scattering experiments on high-quality single crystals of Mn$_{1.4}$PtSn at low temperatures, we evidence how the underlying $D_{2d}$ symmetry of the DMI in this material is reflected in its magnetic texture. Our studies reveal the existence of a novel and complex metastable phase, which possibly has a mixed character of both the N\'{e}el-type cycloid and the Bloch-type helix, that forms at low temperature in zero fields upon the in-plane field training. This hybrid spin-spiral structure has a remarkable tunability, allowing to tilt its orientation beyond high-symmetry crystallographic directions and control its spiral period. These results broaden the reachness of Heusler $D_{2d}$ materials exotic magnetic phase diagram and extend its tunability, thus enhancing a relevant playground for further fundamental explorations and potential applications in energy saving technologies.