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

Abstract

We discuss distinctive features of spiral states in bulk chiral magnets such as MnSi and Cu2OSeO3 that stem from the effect of the cubic magnetocrystalline anisotropy. First of all, at both the helical-to-conical and theconical-to-ferromagnetic transitions, taking place at Hc1 and Hc2, respectively, the cubic anisotropy leads to reversible or irreversible jumplike reorientations of the spiral wave vectors. 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 and thus it can help to understand the magnetic phase diagram of these archetypal skyrmion hosts. In addition, we show that properties of isolated skyrmions such as interskyrmion attraction, orientation, and/or nucleation are also rooted in the properties of host spiral states, in which skyrmions are stabilized