Dielectric relaxation in doped SrTiO_3: Transition from classical thermal activation to quantum tunnelling

摘要

The transition from the thermally activated regime to quantum tunneling is observed in the dielectric relaxation in SrTiO_3 ceramic samples doped with Mn and (MgNb). The relaxation is attributed to Mn_(Ti)~(4+) off-center ions and to polaronlike defects coupled to Mn_(Ti)~(2+) and Nb_(Ti)~(5+) centers. The experimental results are fitted to an Arrhenius relation and to quantum tunneling with the account of damping and phonon-assisted processes.