Imaging small skyrmions at room temperature in Fe-rich Fe_1.2Ge epitaxial films

Chiral magnets exhibit a variety of interesting magnetic phases including topological skyrmion spin textures, a candidate for ultrahigh density memory. A widely studied chiral magnet is FeGe which exhibits skyrmions (∼ 70 nm in diameter) up to its Curie temperature of ∼270 K. To raise the Curie temperature of FeGe and achieve skyrmions at room temperature, we adopted a strategy to develop artificial chiral magnets via atomic-layer molecular beam epitaxy (MBE) far from equilibrium. Specifically, by adding excess Fe atoms to epitaxial FeGe films, we engineered a new Fe-rich Fe_1.2Ge material which has its Curie temperature above room temperature. Magnetic imaging by Magnetic Force Microscopy (MFM) and Lorentz Transmission Electron Microscopy (LTEM) reveal the presence of small skyrmions (<20 nm diameter) at room temperature, two important characteristics for new magnetic memory. Topological Hall effect measurements confirm the topological nature of the observed spin textures.