Skyrmion alignment and pinning effects in the disordered multiphase skyrmion material <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Co</mml:mi><mml:mn>8</mml:mn></mml:msub><mml:msub><mml:mi>Zn</mml:mi><mml:mn>8</mml:mn></mml:msub><mml:msub><mml:mi>Mn</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:mrow></mml:math>
Melissa E. Henderson, Markus Bleuel, J. Beare, David G. Cory, B. Heacock, M. G. Huber, G. M. Luke, M. Pula, Dusan Sarenac, S. Sharma, E. M. Smith, Kirill Zhernenkov, D. A. Pushin
Abstract
Underlying disorder in skyrmion materials may both inhibit and facilitate skyrmion reorientations and changes in topology. The identification of these disorder-induced topologically active regimes is critical to realizing robust skyrmion spintronic implementations, yet few studies exist for disordered bulk samples. Here, we employ small-angle neutron scattering (SANS) and micromagnetic simulations to examine the influence of skyrmion order on skyrmion lattice formation, transition, and reorientation dynamics across the phase space of a disordered polycrystalline ${\mathrm{Co}}_{8}{\mathrm{Zn}}_{8}{\mathrm{Mn}}_{4}$ bulk sample. Our measurements reveal a disordered-to-ordered skyrmion square lattice transition pathway characterized by the promotion of fourfold order in SANS and accompanied by a change in topology of the system, reinforced through micromagnetic simulations. Pinning responses are observed to dominate skyrmion dynamics in the metastable triangular lattice phase, enhancing skyrmion stabilization through a remarkable skyrmion memory effect which reproduces previous ordering processes and persists in zero field. These results uncover the cooperative interplay of anisotropy and disorder in skyrmion formation and restructuring dynamics, establishing tunable pathways for skyrmion manipulation.