Reorientation of (MnTi'-VO••)x defect dipoles in acceptor-modified BaTiO3 single crystals: An electron paramagnetic resonance study

The effect of external electric fields on the orientation of (Mn-Ti(')-V-O(center dot center dot))(x) defect dipoles in ferroelectric BaTiO3 single crystals and its interplay with the domain structure were investigated by means of electron paramagnetic resonance (EPR) spectroscopy and optical microscopy. The results show that in specimens aged in the ferroelectric state for a defined time, so-termed ferroelectrically aged, the (Mn-Ti(')-V-O(center dot center dot))(x) defect dipoles orient along the direction of spontaneous polarization and follow the domain switching upon poling with correspondingly high electric fields. A comparison of the EPR signal in poled aged single-domain samples to that in naturally aged multidomain samples indicates a similar reorientation process of the defect dipole, which means that dipole reorientation rather requires long time, thermal energy, and high electric fields, i.e., more energy.