Surface dependent structural phase transition in SrTiO3 observed with spin relaxation of 8Li

We investigate the 105 K structural phase transition in SrTiO3 using depth controlled measurements of the spin relaxation of 8Li. 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 8Li ( I = 2 ) to hold the nuclear polarization. The tetragonal distortion accompanying the phase transition modifies the \{EFG\} in some 8Li implantation sites, resulting in an observable loss of 8Li polarization. This loss of polarization begins at a temperature T * = 150 K , 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.