Aging in strontium-calcium titanate crystals

The complex dielectric constant ε'(ω, t) of the orientational glass Sr1-xCaxTiO3 (SCT) with x=0.0055 was measured as a function of time at 4.2 K, for frequencies ranging from 1 kHz to 1 MHz, after different thermal histories. Both the in-phase component ε' and the out-of-phase component ε'' clearly exhibit aging as shown by the cooling rate dependence of their evolution. Moreover, a weak dependence has been seen for the asymptotic values of both components at very long time. Hence, evidence exists for ergodicity breaking. This is in contrast to what was seen for spin glasses, and similar to what was observed for the series K1-xLixTaO3 (KLT) of orientational glasses studied previously. However, when temperature jumps are imposed on the SCT sample, the response differs both from that of spin glasses and from that of the KLT series. (author)