Electron spin resonance study of the phase transitions in barium titanate

Abstract

The Fe 3+ EPR spectrum at X-band in BaTiO 3 has been used as a vehicle to study the cubic-tetragonal and tetragonal-orthorhombic phase transitions. There is an abrupt change in the spectrum at both transitions. Since transitions to the tetragonal phase from either of the adjoining phases can be accomplished by the application of a strong electric field, one should be able to produce a considerable change in the EPR spectrum. Previous attempts to do this have not been successful. (5) Operating at temperatures just above the cubic-tetragonal transition, as well as within the temperature hysteresis region of the tetragonal-orthorhombic transition, with properly prepared electrodes we have been able to induce the tetragonal spectrum with an applied electric field. In the absence of a field the transition between orthorhombic and tetragonal phases with increasing temperature s discontinuous. This discrepancy with the spontaneous polarization data is discussed.