Mechanical Loss in Multiferroic Materials at High Frequencies: Friction and the Evolution of Ferroelastic Microstructures

Abstract

Energy absorption in multiferroic materials stems typically from strain relaxation which can be strong even when no extrinsic defects exist in the material. Computer simulations of a simple two-dimensional model on a generic, proper ferroelastic material identify the dissipative mechanisms associated with the dynamical motion as: a) advance and retraction of needle-shaped twin domains and, b) movement of kinks inside twin boundaries. Both movements involve friction losses.

Strain rate dependence of twinning avalanches at high speed impact

“…1(a)), with values similar to results from previous quasistatic simulations. [7][8][9][10] Increasing the strain rate decreases the yield energy from 4 meV/atom at 5 Â 10 À6 s À1 , to 0.5 meV/atom at 5 Â 10 À5 s À1 (Fig. 1(b)), and to values smaller than 0.01 meV/atom at 10 À4 s À1 (Fig.…”

“…The details of properties obtained by this potential are described in our previous work. [7][8][9][10] The equilibrium unit cell is in shape of parallelogram with the shear angle of 4 . We set the equilibrium lattice constant a ¼ 1 Å and atomic mass to M ¼ 100 amu.…”

“…The collective phenomenon of the twin pattern formation is known to progress via avalanches both for the nucleation and progression of twin boundaries. [7][8][9][10] We analyze the energy evolution of the pattern formation during the shear deformation (Fig. 2) and find energy jerks whenever an avalanche forms.…”

“…The yield process was shown previously to follow power law dynamics. [7][8][9][10] The avalanche dynamics of twinning has been investigated experimentally at low strain rates [11][12][13] while little is known for high strain rates. Two questions are tantamount: does the yield process remain scale invariant and if so, does the energy exponent of the power law distribution of the avalanche formation 14 change?…”

Heat transport by phonons and the generation of heat by fast phonon processes in ferroelastic materials

“…3(a)), with values similar to results from previous quasi-static simulations. [31][32][33][34] Increasing the strain rate decreases the yield energy from 4 meV/atom at 5×10 −6 τ −1 , to 0.5 meV/atom at 5×10 −5 τ −1 (Fig. 3(a)), and to values smaller than 0.01 meV/atom at 10 −4 τ −1 (Fig.…”