Unexpectedly Large Skyrmion Topological Hall Effect near Room Temperature in Mesoscopic FeGe*

Magnetic skyrmions are nanometer sized topological spin structures proposed as building blocks of future memory devices with high density and low power consumption. Skyrmions give rise to a Topological Hall Effect (THE) that could be used for detection in memory bits. Even though the stabilization temperature of skyrmions in FeGe is near room temperature, its THE was assumed to be below detection limits because of the larger skyrmion size. I will present the first observation of skyrmion THE near room temperature (276 K, 3 °C) in a mesoscopic lamella extracted from a FeGe crystal with a Focused Ion Beam. This THE has an unexpectedly large magnitude (+5 nΩ.cm), and it unambiguously coincides with the skyrmion lattice revealed by neutron scattering. Hall Effect measurements also point to a reentrant magnetic phase adjacent to the skyrmion phase. We explain the large THE as result of a large normal Hall constant, revealing a new route to enhance THE, a requirement for electrical detection of skyrmions.