Ultrafast magnetoelastic probing of surface acoustic transients

Abstract

We generate in-plane magnetoelastic waves in nickel films using the all-optical transient grating technique. When performed on amorphous glass substrates, two dominant magnetoelastic excitations can be resonantly driven by the underlying elastic distortions, the Rayleigh surface acoustic wave and the surface skimming longitudinal wave. An applied field, oriented in the sample plane, selectively tunes the coupling between magnetic precession and one of the elastic waves, thus demonstrating selective excitation of coexisting, large-amplitude magnetoelastic waves. Analytical calculations based on the Green's function approach corroborate the generation of multiple surface acoustic transients with disparate decay dynamics.

Strain and Thermally Induced Magnetic Dynamics and Spin Current in Magnetic Insulators Subject to Transient Optical Grating

“…The elastic wave excites resonantly the magnetization dynamics and magnonic spin current near the ferromagnetic resonance frequency. This prediction is in line with the recent experiments reported by Janušonis et al (2015Janušonis et al ( , 2016. Furthermore, we identify a magnonic spin current flowing perpendicular to the film surface plane, i.e., perpendicular to the propagation direction of the elastic waves.…”

“…The periodic function cos 2 (2πx/r l ) describes the effect of the transient grating. The grating period r l /2 is tunable by the phase difference between the two laser beams (Etesami et al, 2015;Janušonis et al, 2015Janušonis et al, , 2016. The profile of laser intensity I is shown in Figure 2 for r l = 2.8 µm.…”

“…Here, ω = 2πf is the wave frequency, and k is the wave vector. The wave is only located in the film surface due to the form of the temperature profile (Janušonis et al, 2015(Janušonis et al, , 2016. The wave-vector is determined by the period of the transmitted grating k = 4π/r l , and the frequency is a function of the wave-vector f = v Λ with v ≈ 5,600 m/s.…”

“…A further interesting method to induce magnetoelastic excitations via electric fields is to use multiferroics materials, particularly heterostructures of coupled piezoelectric or ferroelectric and ferromagnetic layers (Vaz, 2012;Cherepov et al, 2014;Jia et al, 2014Jia et al, , 2016Gilbert et al, 2016). In recent experiments (Janušonis et al, 2015(Janušonis et al, , 2016, a transient optical grating is generated on the surface of a ferromagnet by two phase-locked interfering laser pulses. On the length scale of the interference pattern, a frequency tunable elastic wave is generated.…”

Frequency and magnetic field mapping of magnetoelastic spin pumping in high overtone bulk acoustic wave resonator

“…[1][2][3][4][5][6][7][8][9][10][11] In particular, much attention is given to acoustically driven (AD) excitation of magnetic oscillations in artificial multiferroic structures due to strain mediated coupling between the microwave electric field in a piezoelectric layer and magnetization in a ferromagnetic layer. [6][7][8][9][10][11] In the field of microwave spintronics, acoustic spin pumping (ASP) is the generation of spinpolarized electron currents in normal metal from AD magnetization precession in an attached magnetic material.…”