Ageing and Memory in PLZT Above the Polar Freezing Temperature

We measured the dielectric susceptibility (200 Hz–1 MHz) and elastic compliance (1–10 KHz) of PLZT 9/65/35 with different cooling/heating protocols. By stopping the cooling run at a temperature T ₁ , ageing was found as a decrease in both dielectric and elastic susceptibilities, with a dependence on time almost logarithmic. On further cooling, the reference curve measured during a continuous run was rejoined, a phenomenon known as rejuvenation. The processes could be repeated at several T_n < T ₁ , and the susceptibilities measured on heating partially retraced the dips formed during the ageing stages at the various T_n. All these phenomena, including the memory of multiple ageing stages, are well known in magnetic spin-glasses below the freezing temperature of the magnetic fluctuations. Here we show that PLZT 9/65/35 exhibits memory of several ageing stages also above the temperature of the maximum of the dynamic susceptibility.

Keywords:

• PLZT
• relaxor
• memory
• ageing
• anelastic spectroscopy
• dielectric spectroscopy

PACS:

• 77.84.Dy
• 62.40.+i
• 75.10.Nr

Acknowledgments

Financial support from the POLECER network is gratefully acknowledged.