Disordered skyrmion phase stabilized by magnetic frustration in a chiral magnet

TL;DR

This study discovers a disordered skyrmion phase in a chiral magnet, stabilized by magnetic frustration and Dzyaloshinskii-Moriya interaction, revealing a new form of topological spin texture in a complex alloy.

Contribution

It reports the first observation of a three-dimensionally disordered skyrmion phase stabilized by magnetic frustration in a chiral magnet alloy.

Findings

Identification of two distinct skyrmion phases in Co7Zn7Mn6

Disordered skyrmion phase stable well below T_c

Interplay between chiral and frustrated magnetism enhances skyrmion stability

Abstract

Magnetic skyrmions are vortex-like topological spin textures often observed to form a triangular-lattice skyrmion crystal in structurally chiral magnets with Dzyaloshinskii-Moriya interaction. Recently $\beta$-Mn structure-type Co-Zn-Mn alloys were identified as a new class of chiral magnet to host such skyrmion crystal phases, while $\beta$-Mn itself is known as hosting an elemental geometrically frustrated spin liquid. Here we report the intermediate composition system Co$_7$Zn$_7$Mn$_6$ to be a unique host of two disconnected, thermal-equilibrium topological skyrmion phases; one is a conventional skyrmion crystal phase stabilized by thermal fluctuations and restricted to exist just below the magnetic transition temperature $T_\mathrm{c}$, and the other is a novel three-dimensionally disordered skyrmion phase that is stable well below $T_\mathrm{c}$. The stability of this new disordered skyrmion phase is due to a cooperative interplay between the chiral magnetism with Dzyaloshinskii-Moriya interaction and the frustrated magnetism inherent to $\beta$-Mn.