Photoexcitation of gigahertz longitudinal and shear acoustic waves in BiFeO3 multiferroic single crystal

Abstract

Using femtosecond laser pulses, coherent GHz acoustic phonons are efficiently photogenerated and photodetected in BiFeO3 (BFO) multiferroic single crystal. Due to the crystal lattice symmetry, longitudinal as well as two transverse acoustic modes are generated and detected, and the corresponding sound velocities are determined. This provides the opportunity to experimentally evaluate the elastic coefficients of the multiferroic compound BiFeO3 that have been estimated so far only through ab initio calculations. The knowledge of the elastic properties of BFO is highly desired for BFO integration in nanoelectronic devices. Moreover, our findings highlight also that BFO may be a good candidate for light-controlled coherent acoustic phonons sources.

Strain modulated transient photostriction in La and Nb codoped multiferroic BiFeO3 thin films

“…25 The oscillation frequency remains unchanged with increasing pump fluence, while the amplitude of the oscillation is proportional to the pump fluence. For these thin film samples, we do not identify the transverse acoustic (TA) phonons, which has been observed on [010] direction for rhombohedral symmetry of BFO single crystal.…”

“…According to the strain pulse propagation model, [25][26][27][28] the phonon dispersion is 2pX ¼ v Sound q. Thus, the sound velocity in the sample is given by…”

“…. 25 Using the mass density q BFO ¼ 8340 kg m À3 , the magnitudes of C ? of BLFNO films on different substrates can be estimated.…”

“…For these thin film samples, we do not identify the transverse acoustic (TA) phonons, which has been observed on [010] direction for rhombohedral symmetry of BFO single crystal. 25 The transient reflectivity changes without the relaxation background can be fitted by a damped harmonic function As the wave-vector conservation in back-scattered configuration, the wave-vector of the acoustic wave q ¼ 2k probe , where k probe is the wave-vector of the probe beam with…”

Ultrafast carrier dynamics and radiative recombination in multiferroic BiFeO3single crystals and thin films

“…Despite the intense research on this material, relatively few studies of its ultrafast dynamics have been done to date [4][5][6][7]. Previously, we have studied carrier relaxation and recombination in BFO single crystals up to 800 K by using ultrafast optical (UOS) and photoluminescence (PL) spectroscopies [5].…”