Electron paramagnetic resonance of Mn 4+ in BaTiO 3

Abstract

The Electron Paramagnetic Resonance (EPR) of Mn 4+ in the rhombohedral low- temperature phase of BaTiO 3 has been observed at 19.3 and 13.0 GHz. The spectra have axial symmetry along 〈111〉 directions. Intensity measurements prove that the Mn 4+ EPR reflects {111} domain orientation. The spin-Hamiltonian constants are g ‖=1.9968(19), g ‖=2.0015(5), A ‖=67.48(5)×10 −4 cm −1, A ‖=73.04(15)×10 −4cm −1, and D=0.65(1)cm −1 at 4.2 K. The very large D value is more than 20 times that found for the isoelectronic Cr 3+. The latter ion remains centered in its surrounding octahedral oxygen cage, whereas the Mn 4+ is off-center with similar coordinates as Ti 4+. This result is deduced from a superposition-model analysis.