On the origin of perpendicular magnetic anisotropy in STO/Co/X (X = Pd, Pt) sputtered films

Non-magnetic oxide/Co-based heterostructures with perpendicular magnetic anisotropy (PMA) are highly attractive for energy-efficient spintronic applications, owing to the tunability of their magnetic properties via external electric fields. SrTiO3 (STO)/Co systems, in particular, offer strong potential due to the high dielectric constant of STO, which enables efficient voltage control of interfacial magnetism by interface charge accumulation. Although PMA has been previously observed, its microscopic origin remains unclear. Here, we investigate the mechanism responsible for PMA in Co/X (X = Pd, Pt) thin films on STO(1 1 1) and STO(1 0 0) substrates with mixed terminations. The results indicate a strong influence of STO orientation, reflected in different surface reactivity, as well as of the nature of the capping layer. These findings shed light on the interfacial factors that control PMA in STO/Co/X (X = Pd, Pt) heterostructures, suggesting that optimal PMA can be achieved by employing STO(1 1 1) substrates with a pure SrO34- termination, thereby enabling the development of advanced energy-efficient spintronic devices.