Electron paramagnetic resonance studies of manganese centers in SrTiO3: Non-Kramers Mn3+ ions and spin-spin coupled Mn4+ dimers

An X- and Q-band electron paramagnetic resonance (EPR) study is reported on SrTiO3 single crystals doped with 0.5 at. % MnO. The EPR spectra originating from the S = 2 ground state of the Mn3+ ions are shown to belong to three distinct types of Jahn-Teller centers. The ordering of the oxygen vacancies due to the reduction treatment of the samples and the consequent formation of an oxygen vacancy associated with the Mn3+ centers is explained in terms of the localized charge compensation. The EPR spectra of the SrTiO3:Mn crystals show the presence of next-nearest-neighbor exchange coupled Mn4+ pairs in the 〈110〉 directions.