Tilted spirals and low-temperature skyrmions in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>Cu</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>OSeO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>
M. Crisanti, Andrey O. Leonov, R. Cubitt, Ankit Labh, H. Wilhelm, Marcus Schmidt, C. Pappas
Abstract
The bulk helimagnet ${\mathrm{Cu}}_{2}{\mathrm{OSeO}}_{3}$ represents a unique example in the family of B20 cubic helimagnets exhibiting a tilted spiral and skyrmion phase at low temperatures when the magnetic field is applied along the easy $\ensuremath{\langle}001\ensuremath{\rangle}$ crystallographic direction. Here we present a systematic study of the stability and ordering of these low-temperature magnetic states. We focus our attention on the temperature and field dependencies of the tilted spiral state that we observe persisting up to above $T=35 \mathrm{K}$, i.e., up to higher temperatures than reported so far. We discuss these results in the frame of the phenomenological theory introduced by Dzyaloshinskii in an attempt to reach a quantitative description of the experimental findings. We find that the anisotropy constants, which are the drivers behind the observed behavior, exhibit a pronounced temperature dependence. This explains the differences in the behavior observed at high temperatures (above $T=18 \mathrm{K}$), where the cubic anisotropy is weak, and at low temperatures (below $T=18 \mathrm{K}$), where a strong cubic anisotropy induces an abrupt appearance of the tilted spirals out of the conical state and enhances the stability of skyrmions.