Magnetotransport behavior of LaAlO$_3$/SrTiO$_3$ and Ar-irradiated SrTiO$_3$: implications on Rashba Spin-Orbit coupling and magnetism in quasi-2-dimensional electron gases*

Quasi 2-dimensional electron gases (Q2DEG) in complex oxide heterostructures exhibit a wide range of tunable behavior that promises potentially new functionalities. In particular much interest has focused on the Q2DEG at the LaAlO$_3$/SrTiO$_3$ interface, where evidence for Rashba spin-orbit coupling and magnetic behavior has recently been found through magnetotransport measurements. At present it is unclear whether the spin-orbit and magnetic effects are unique to the LaAlO$_3 $/SrTiO$_3$ interface, or if they arise from the properties of doped SrTiO$_3$. In order to shed light on this issue, we compare the magnetotransport properties of LaAlO$_3$/SrTiO$_3$ and Ar$^+$-irradiated SrTiO$_3$. Strikingly similar magnetotransport behavior is observed between LaAlO$_3$/SrTiO$_3 $ and Ar$^+$-irradiated Q2DEGs. However, our analysis indicates changes in the confinement or thickness of the Q2DEG can account for the magnetotransport observed. Implications of our results on Rashba spin-orbit coupling and magnetism at the LaAlO$_3$/SrTiO$_3$ interface will be discussed.