Spin-orbit interaction and Kondo scattering at the PrAlO3/SrTiO3 interface: effects of oxygen content

We report the effects of oxygen pressure during growth (P-O2) on the electronic and magnetic properties of PrAlO3 films grown on TiO2-terminated SrTiO3 substrates. Resistivity measurements show an increase in the sheet resistance as P-O2 is increased. The saturation of the sheet resistance down to 0.3 K is consistent with Kondo theory for P-O2 >= 10(-5) torr. Resistivity data fits indicate Kondo temperatures of 16-18 K. For the 10(-4) sample, we measured a moderate positive magnetoresistance (MR) due to a strong spin-orbit (SO) interaction at low magnetic fields that evolves into a larger negative MR at high fields due to the Kondo effect. Analysis of the MR data permitted the extraction of the SO interaction critical field for the P-O2 = 10(-5) torr interface (H-SO = 1.25 T). We observed high positive MR for the least oxygenated sample, where a fraction of the n-type carriers are derived from oxygen vacancies and possible cation interdiffusion; for this 6 x 10(-6) torr sample, Hall effect data indicate a thick conducting layer. Its extremely high MR (similar to 400%) is attributed to classical behavior due to a distribution of mobilities.