Observation of Nano Sized Effect on EPR of Mn4+ and Cr3+ in SrTiO3 Powders

The chromium doped SrTiO3 nanopowders with particles size of 100, 50, 20nm sizes have been synthesized and studied by Electron Paramagnetic Resonance (EPR). Along with chromium impurity it was found the powder contained small concentration of manganese as a residential impurity. Mn4+ ions on Ti4+ lattice sites were identified, with spin-Hamiltonian parameters closed to even in the bulk material. It was found that the linewidth depends on particle size. This effect may be traced back to changes of the small parameter of fine structure D due to its dependence on the particle size of the individual nanocrystallite. It seems, the most of Cr3+ ions did not substitute for Ti4+ and form some phase at the surface of SrTiO3 particles.