Pinning of Helimagnetic Phase Transitions in Zn-Substituted Skyrmion Host Cu${}_2$OSeO${}_3$

Abstract

Magnetic skyrmions are nano-sized topological spin textures stabilized by a delicate balance of magnetic energy terms. The chemical substitution of the underlying crystal structure of skyrmion-hosting materials offers a route to manipulate these energy contributions, but also introduces additional effects such as disorder and pinning. While the effects of doping and disorder have been well studied in B20 metallic materials such as Fe${}_{1-x}$Co${}_x$Si and Mn${}_{1-x}$Fe${}_x$Si, the consequences of chemical substitution in the magnetoelectric insulator Cu${}_2$OSeO${}_3$ have not been fully explored. In this work, we utilize a combination of AC magnetometry and small angle neutron scattering to investigate the magnetic phase transition dynamics in pristine and Zn-substituted Cu${}_2$OSeO${}_3$. The results demonstrate that the first order helical-conical phase transition exhibits two thermally separated behavioural regimes: at high temperatures, the helimagnetic domains transform by large-scale, continuous rotations, while at low temperatures, the two phases coexist. Remarkably, the effects of pinning in the substituted sample are less prevalent at low temperatures, compared to high temperatures, despite the reduction of available thermal activation energy. We attribute this behaviour to the large, temperature-dependent, cubic anisotropy unique to Cu${}_2$OSeO${}_3$, which becomes strong enough to overcome the pinning energy at low temperatures. Consideration and further exploration of these effects will be crucial when engineering skyrmion materials towards future applications.

References in corpus (18)

• Spontaneous Skyrmion Ground States in Magnetic Metals
• A new class of chiral materials hosting magnetic skyrmions beyond room temperature
• Skyrmion-skyrmion and skyrmion-edge repulsions in skyrmion-based racetrack memory
• Observation of two independent skyrmion phases in a chiral magnetic material
• A.C. susceptibility as a probe of low-frequency magnetic dynamics
• Real-Space and Reciprocal-Space Berry Phases in the Hall Effect of Mn${}_{1-\mathrm{x}}$Fe${}_{\mathrm{x}}$Si
• Skyrmion formation in a bulk chiral magnet at zero magnetic field and above room temperature
• Metastable skyrmion lattices governed by magnetic disorder and anisotropy in $\beta$-Mn-type chiral magnets
• Spin-wave spectroscopy on Dzyaloshinskii-Moriya interaction in room-temperature chiral magnets hosting skyrmions
• Current-induced viscoelastic topological unwinding of metastable skyrmion strings
• Thermodynamic evidence of a second skyrmion lattice phase and tilted conical phase in Cu${}_2$0SeO${}_3$
• Magnetic relaxation phenomena in the Chiral Magnet Fe${}_{1-x}$Co${}_x$Si: An ac susceptibility study
• A strategy for the design of skyrmion racetrack memories
• Extended skyrmion lattice scattering and long-time memory in the chiral magnet Fe${}_{1-x}$Co${}_x$Si
• Dissipation processes in the insulating skyrmion compound Cu2OSeO3
• Measuring the Formation Energy Barrier of Skyrmions in Zinc Substituted Cu${}_2$OSeO${}_3$
• Magnetism and Néel skyrmion dynamics in GaV${}_4$S${}_{8-y}$Se${}_y$
• Increasing the skyrmion stability in Cu${}_2$OSeO${}_3$ by chemical substitution

Cited by in corpus (5)

• Field-driven metamorphoses of isolated skyrmions within the conical state of cubic helimagnets
• Skyrmion Alignment and Pinning Effects in a Disordered Multi-Phase Skyrmion Material Co8Zn8Mn4
• Experimental Evidence of a change of Exchange Anisotropy Sign with Temperature in Zn-Substituted Cu2OSeO3
• Effect of chemical substitution on the skyrmion phase in Cu${}_2$OSeO${}_3$
• Bloch point-mediated skyrmion annihilation in three dimensions