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. P₁ and P₂ almost overlap for first order phase transitions. P₁, 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, ε' or ΔJ/J, always shows a high plateau below T_c 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 T_c superconductors