Characterization of a Disordered above Room Temperature Skyrmion Material Co8Zn8Mn4.

Melissa E Henderson,Pat Clancy,Graeme M Luke,David G Cory,Evan M Smith,Casey A Marjerrison,James Beare,Michael G Huber,Sudarshan Sharma,Kirill Zhernenkov,Mathew Pula,Dusan Sarenac,Dmitry A Pushin,Markus Bleuel

doi:10.3390/ma14164689

Abstract

Topologically nontrivial spin textures host great promise for future spintronic applications. Skyrmions in particular are of burgeoning interest owing to their nanometric size, topological protection, and high mobility via ultra-low current densities. It has been previously reported through magnetic susceptibility, microscopy, and scattering techniques that CoZnMn forms an above room temperature triangular skyrmion lattice. Here, we report the synthesis procedure and characterization of a polycrystalline CoZnMn disordered bulk sample. We employ powder X-ray diffraction and backscatter Laue diffraction as characterization tools of the crystallinity of the samples, while magnetic susceptibility and Small Angle Neutron Scattering (SANS) measurements are performed to study the skyrmion phase. Magnetic susceptibility measurements show a dip anomaly in the magnetization curves, which persists over a range of approximately 305 K–315 K. SANS measurements reveal a rotationally disordered polydomain skyrmion lattice. Applying a symmetry-breaking magnetic field sequence, we were able to orient and order the previously jammed state to yield the prototypical hexagonal diffraction patterns with secondary diffraction rings. This emergence of the skyrmion order serves as a unique demonstration of the fundamental interplay of structural disorder and anisotropy in stabilizing the thermal equilibrium phase.

Highlights

Protected states are ubiquitous in nature, appearing in disparate physical systems spanning condensed matter phases, such as liquid crystals [1], to cosmological strings [2]
Manifesting as quasiparticle nanoscale magnetic spin configurations with a whirling vortex-like structure in magnetic textures, their integer topological charges equate to a nontrivial mapping of the magnetization from real space to the order parameter space of the two-dimensional unit sphere [7]
This countable “winding” property gives rise to Berry curvatures, which can be expressed in terms of the emergent electric and magnetic fields, wherein each skyrmion tube corresponds to one quantum of the emergent magnetic flux [8]

Summary

Introduction

Protected states are ubiquitous in nature, appearing in disparate physical systems spanning condensed matter phases, such as liquid crystals [1], to cosmological strings [2]. A myriad of exotic long-period chiral structures/phases have since been realized in the Co-Zn-Mn series, ranging from meron-antimeron lattices generated by in-plane magnetic anisotropy [38] to disconnected low-temperature disordered skyrmion phases stabilized by frustrated interactions [37].

Results

Conclusion