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), enabling thermally stabile memory cells 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 an external field during the switching limits its practical application, and therefore field-free switching of L10-FePt is highly demanded. In this manuscript, by growing the L10-FePt film on vicinal MgO (001) substrates, we realize the field-free switching of L10-FePt. 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. The dependence on the vicinal angle, film thickness, and growth temperature demonstrates a wide operation window for the field-free switching of L10-FePt. We confirm the physical origin of the field-free switching is due to the tilted anisotropy of L10-FePt induced by the vicinal surface. We also quantitatively characterize the spin-orbit torques in the L10-FePt films. Our results extend beyond the established strategies to realize field-free switching, and potentially could be applied to mass production.