Twinning and lattice distortions in the epitaxy of La _0.67 Sr _0.33 MnO ₃ thin films on (0 0 1) SrTiO ₃

We study the epitaxy of La _0.67 Sr _0.33 MnO ₃ (LSMO) thin films on SrTiO ₃ (STO) (0 0 1) by pulsed laser deposition (PLD). In addition to a lattice mismatch of 0.82%, ferromagnetic LSMO is rhombohedral (pseudo-cubic with an angle of 90.26°) while STO is cubic. We measure lattice distortions using quantitative high resolution electron microscopy (HRTEM). For low thickness far below the critical one, such distortions allow a partial recovery of the original rhombohedral symmetry of LSMO [R. Lyonnet et al., Appl. Surf. Sci. 162-163 (2000) 245]. Here, we present observations of layers of various thickness and further characterisation of this phenomenon as a function of misorientation of the substrate surface.