Direct evidence for off-centering of Mn impurity in SrTiO3

Mn-doped SrTiO3 samples (3% Mn) with different deviations from stoichiometry have been investigated using XAFS spectroscopy. It was shown the under various preparation conditions manganese atoms can sub-stitute A and B sites of the perovskite structure and are in them in different charge states. Impurity Mn4+ ions that substitute Ti sites occupy on-center position in the lattice, whereas Mn2+ ions that substitute Sr sites are off-center and are displaced from the lattice sites by a distance of 0.32.