Large Rashba spin–orbit coupling in metallic SrTaO₃ thin films

Abstract We fabricated conductive SrTaO 3 epitaxial films on insulator substrates and measured the Rashba parameter using weak anti-localization analysis. The Rashba parameter, reaching up to 9.9 × 10 −13 eVm, is the highest among metallic oxides and is comparable to the LaAlO 3 /SrTiO 3 interface, which is widely used in Rashba effect studies. This indicates the potential for oxide-based spintronic devices. To use them as devices, it is important to investigate how film thickness affects the resistivity. Films ranging from 8.6 to 25 nm exhibited metallic conduction, but those thicker than 25 nm showed an unexpected increase in resistivity, suggesting instability of the meta-stable Ta 4+ state.