Large Rashba parameter for 4d strongly correlated perovskite oxide SrNbO3 ultrathin films

To elucidate the spin relaxation mechanism of $\mathrm{SrNb}{\mathrm{O}}_{3}$ (SNO) ultrathin films, the transport properties of a series of SNO films with various thicknesses $t$ were measured on both sides of the metal-insulator transition. The spin-orbit scattering time (${\ensuremath{\tau}}_{\mathrm{so}}$) was deduced from the analysis of the magnetoresistance with weak antilocalization theory, and it was found that ${\ensuremath{\tau}}_{\mathrm{so}}$ was inversely proportional to the momentum scattering time. This result was explained in terms of the D'Yakonov-Perel mechanism, indicative of the dominant Rashba effect. The values of the Rashba parameter, on the order of $1\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}12}$ eV m were the largest in the values reported for other ultrathin films of metallic oxides.