Metastable skyrmion lattices governed by magnetic disorder and anisotropy in $\beta$-Mn-type chiral magnets

Abstract

Magnetic skyrmions are vortex-like topological spin textures often observed in structurally chiral magnets with Dzyaloshinskii-Moriya interaction. Among them, Co-Zn-Mn alloys with a $\beta$-Mn-type chiral structure host skyrmions above room temperature. In this system, it has recently been found that skyrmions persist over a wide temperature and magnetic field region as a long-lived metastable state, and that the skyrmion lattice transforms from a triangular lattice to a square one. To obtain perspective on chiral magnetism in Co-Zn-Mn alloys and clarify how various properties related to the skyrmion vary with the composition, we performed systematic studies on Co${}_{10}$Zn${}_{10}$, Co${}_9$Zn${}_9$Mn${}_2$, Co${}_8$Zn${}_8$Mn${}_4$ and Co${}_7$Zn${}_7$Mn${}_6$ in terms of magnetic susceptibility and small-angle neutron scattering measurements. The robust metastable skyrmions with extremely long lifetime are commonly observed in all the compounds. On the other hand, preferred orientation of a helimagnetic propagation vector and its temperature dependence dramatically change upon varying the Mn concentration. The robustness of the metastable skyrmions in these materials is attributed to topological nature of the skyrmions as affected by structural and magnetic disorder. Magnetocrystalline anisotropy as well as magnetic disorder due to the frustrated Mn spins play crucial roles in giving rise to the observed change in helical states and corresponding skyrmion lattice form.

70 pages, 19 figures

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Cited by in corpus (22)

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• A theory of skyrmion crystal formation
• Nonreciprocal Phonon Propagation in a Metallic Chiral Magnet
• Skyrmion Alignment and Pinning Effects in a Disordered Multi-Phase Skyrmion Material Co8Zn8Mn4
• Characterization of a Disordered Above Room Temperature Skyrmion Material Co8Zn8Mn4
• Structural transition of skyrmion quasiparticles under compression
• Anomalous electrical transport and magnetic skyrmions in Mn-tuned Co9Zn9Mn2 single crystals
• Pinning of Helimagnetic Phase Transitions in Zn-Substituted Skyrmion Host Cu${}_2$OSeO${}_3$
• Spin wave stiffness and damping in a frustrated chiral helimagnet Co${}_8$Zn${}_8$Mn${}_4$ as measured by small-angle neutron scattering
• Controllable inter-skyrmion attractions and resulting skyrmion-lattice structures in two-dimensional chiral magnets with in-plane anisotropy
• Direct observation of the exchange anisotropy in the helimagnetic insulator Cu${}_2$OSeO${}_3$
• Nonreciprocal transport in a room-temperature chiral magnet
• Does carrier localization affect the anomalous Hall effect?
• Skyrmion crystal with integer and fractional skyrmion numbers in a nonsymmorphic lattice structure with the screw axis
• Robustness of topological magnons in disordered arrays of skyrmions
• Checkerboard bubble lattice formed by octuple-period quadruple-$Q$ spin density waves
• Anisotropy-dependent decay of room temperature metastable skyrmions and a nascent double-$q$ spin texture in Co${}_8$Zn${}_9$Mn${}_3$
• X-ray holographic imaging of magnetic surface spirals in FeGe lamellae
• Vital role of anisotropy in cubic chiral skyrmion hosts
• Observation of magnetic skyrmion lattice in Cr${}_{0.82}$Mn${}_{0.18}$Ge by small-angle neutron scattering
• Field-induced transformation between triangular and square skyrmion crystals in a tetragonal polar magnet
• Finite-temperature stability of skyrmion crystals in frustrated magnets: Role of sixfold anisotropy and uniform spin mode in momentum space