Field and anisotropy driven transformations of spin spirals in cubic skyrmion hosts

TL;DR

This paper explores how cubic magneto-crystalline anisotropy influences the behavior and phase transitions of spiral magnetic states in bulk chiral magnets, providing insights into skyrmion host materials.

Contribution

It reveals the effects of cubic anisotropy on spiral state reorientations, phase transitions, and the emergence of oblique spirals, guiding future experimental investigations.

Findings

Cubic anisotropy causes jump-like reorientations at magnetic phase transitions.

Interplay of anisotropies leads to elliptically distorted conical states.

Properties of skyrmions are linked to host spiral states.

Abstract

We discuss distinctive features of spiral states in bulk chiral magnets such as MnSi and Cu$_2$OSeO$_3$ that stem from the effect of the cubic magneto-crystalline anisotropy. First of all, at both the helical-to-conical and the conical-to-ferromagnetic transitions, taking place at H$_{c1}$ and H$_{c2}$, respectively, the cubic anisotropy leads to reversible or irreversible jump-like reorientations of the spiral wavevectors. The subtle interplay between the easy and hard anisotropy axes gives rise to a phase transition between elliptically distorted conical states almost without any detectable change in the period. We show that the competition between on-site cubic and exchange anisotropy terms can also lead to oblique spiral states. Our work gives clear directions for further experimental studies to reveal theoretically predicted spiral states in cubic helimagnets beyond the aforementioned well-established states thus, can help to understand the magnetic phase diagram of these archetypal skyrmion hosts. In addition, we show that properties of isolated skyrmions such as inter-skyrmion attraction, orientation and/or nucleation are also rooted in the properties of host spirals states, in which skyrmions are stabilized.