Effects of Disorder on the Skyrmion Phase in FeGe Thin Films*

Magnetic skyrmions are nanoscale whirlpools of magnetic moments that arise certain magnetic materials and are potentially useful as information carriers in next-generation low-energy spintronic devices. To exploit skyrmions in spintronics, we must be able to controllably manipulate them, which necessitates understanding how to create, annihilate, and move them. It also requires understanding how the skyrmion lattice is affected by disorder, dictating how skyrmions will either maneuver around or be pinned by energy barriers within the material’s disorder landscape. Here, we report on the effects of point disorder on the skyrmion phase in epitaxial FeGe thin films. To tune defect densities, we irradiate the films with 2.8 MeV Au ions, varying the dose to control the densities of induced vacancies. We additionally conduct electrical transport measurements, identifying the skyrmion phase by the appearance of a topological Hall effect component, and compare the subsequently constructed field H – temperature T phase diagrams of the irradiated and pristine samples to systematically observe disorder-induced changes in the skyrmion lattice phase.