Surface Dependent Structural Phase Transition in SrTiO3Observed with Spin Relaxation of Li M. Smadella

We investigate the 105K structural phase transition in SrTiO3 using depth controlled measurements of the spin relaxation of Li. The measurements were performed in zero external magnetic field and rely on the local electric field gradient (EFG) at the crystalline implantation site of the Li (I = 2) to hold the nuclear polarization. The tetragonal distortion accompanying the phase transition modifies the EFG in some Li implantation sites, resulting in an observable loss of Li polarization. This loss of polarization begins at a temperature T ∗ = 150K, indicating there is some loss of cubic symmetry well above the bulk transition. We find that the value of T ∗ is unaffected by the range of implantation depths available (10 150 nm), however the temperature dependence of the polarization depends on the surface preparation of the SrTiO3 sample.