Mechanical and Dielectric Energy Loss Related to Viscous Motion and Freezing of Domain Walls

Abstract

Three dielectric loss (D) and/or three mechanical loss (Q -1 ) peaks (P1,P2,P3) and corresponding susceptibilities for ferroelectric KDP and TGS, and ferroelastic LNPP crystal and Cu-Al-Zn-Ni alloy have been investigated in the kHz range. P 1 and P 2 almost overlap for first order phase transitions. P i , a very narrow peak, is attributed to the dynamic domains due to fluctuations near Tc. P2 is recognized to be related to domain walls (DWs). The formulas of Q -1 and D caused by the viscous motion of DWs are derived, being fairly coincident with the experimental data of P2. The viscous coefficient, pinning force constant of DW and the spontaneous shear strain have been calculated for Cu-Al-Zn-Ni. The susceptibility, e' or ΔJ/J, always shows a high plateau below Tc and drops down rapidly nearly consistent with the low temperature side of P3 peak for poly-domain TGS, KDP and Cu-Al-Zn-Ni. P3 is thought to originate from the freezing of DWs of high density due to a collective pinning of randomly distributed defects, similar to the pinned-vortex glass model suggested for high Tc superconductors.