Field free switching through bulk spin-orbit torque in L10-FePt films deposited on vicinal substrates

Abstract

L10-FePt distinguishes itself for its ultrahigh perpendicular magnetic anisotropy (PMA), which enables memory cells with sufficient thermal stability to scale down to 3 nm. The recently discovered "bulk" spin-orbit torques in L10-FePt provide an efficient and scalable way to manipulate the L10-FePt magnetization. However, the existence of external field during the switching limits its practical application, and therefore field-free switching of the L10-FePt is in highly demand. In this manuscript, we demonstrate the field-free switching of the L10-FePt by growing it on vicinal MgO (001) substrates. This method is different from previously established strategies, as it does not need to add other functional layers or create asymmetry in the film structure. We demonstrate the field-free switching is robust and can withstand strong field disturbance up to ~1 kOe. The dependence on vicinal angle, film thickness, and growth temperature demonstrated a wide operation window for the field-free switching of the L10-FePt. We confirmed that the physical origin of the field-free switching is the vicinal surface-induced the tilted anisotropy of L10-FePt. We quantitatively characterize the spin-orbit torques in the L10-FePt films, and found the spin-orbit torques are not significantly influenced by the lattice strain from vicinal substrates. Our results extend beyond the established strategies to realize field-free switching, and potentially could be applied to other magnetic and antiferromagnetic systems.