Magnetic Skyrmionic Bubbles at Room Temperature and Sign Reversal of the Topological Hall Effect in a Layered Ferromagnet Cr0.87Te.

Abstract

The search for materials that exhibit topologically protected spin configurations, such as magnetic skyrmions, continues to be fueled by the promise of outstanding candidate components for spin-based applications. In this study, in situ Lorentz transmission electron microscopy directly images Bloch-type magnetic skyrmionic bubbles in a layered ferromagnet Cr0.87Te single crystal. Owing to the competition between a magnetic dipole interaction and uniaxial easy axis anisotropy, nanoscale magnetic bubbles with random chirality can be observed in a wide temperature range covering room temperature when the external magnetic field is applied along the out-of-plane direction. Moreover, high-density and stable skyrmionic bubbles are successfully realized at zero magnetic field by appropriate field-cooling manipulation. Additionally, a sign reversal of the Hall effect and the derived topological Hall effect is observed and discussed. As quasi-two-dimensional materials, the binary chromium tellurides hosting magnetic skyrmions could have many applications in low-dimensional skyrmion-based spintronic devices in an ambient atmosphere.