Elastic properties assessment in the multiferroic BiFeO3 by pump and probe method

TL;DR

This study uses pump and probe spectroscopy to measure and analyze the elastic properties of bulk BiFeO3, determining all elastic constants and phonon polarization through acoustic wave velocity measurements.

Contribution

It introduces a comprehensive method combining experimental measurements and theoretical calculations to fully characterize the elastic constants of BiFeO3.

Findings

All six elastic constants of BiFeO3 were determined.

Wave velocities enabled unambiguous phonon polarization assignment.

Surface and volume wave propagation depend on direction, revealing anisotropic elastic behavior.

Abstract

We have performed elasticity measurements in the bulk multiferroic BiFeO3 (BFO) using acoustical pump and probe spectroscopy. The sound velocities of the (quasi)-longitudinal and of the two (quasi)-transverse acoustic waves along three independent directions of the (110) surface have been measured. Moreover, one surface wave and one longitudinal wave propagating perpendicular to the surface have been detected. Based on initial input values of the six independent Cij elastic constants determined by our density functional theory calculations and our eleven experimental velocities, the numerical resolution of the acoustic equations allows to determine all the Cij elastic constants of BFO. The propagation direction dependence of volume and surface waves phase velocities allows the unambiguously assignment of the waves, hence the polarization of phonons.