Frequency tunable surface magneto elastic waves

Abstract

We use the transient grating technique to generate narrow-band, widely tunable, in-plane surface magnetoelastic waves in a nickel film. We monitor both the structural deformation of the acoustic wave and the accompanying magnetic precession and witness their intimate coupling in the time domain. Strikingly, when an in plane magnetic field is applied parallel to the acoustic propagation direction, we witness its resonant coupling to the ferromagnetic resonance. V

Ultrafast changes of magnetic anisotropy driven by laser-generated coherent and noncoherent phonons in metallic films

“…[13] as a possible impact for triggering the magnetization precession. Later, coherent phonons have been shown to be an efficient stimulus for changing the MCA in experiments with picosecond strain pulses, when the magnetization precession is excited without direct optical excitation of the ferromagnet [14,15], and with optically excited surface acoustic waves [16,17]. In these experiments, the amplitude of the precession was large enough that we can assume that the coherent phonons may also have a significant contribution when the metal ferromagnet is excited directly by an optical pulse.…”

Ultrafast magnetoelastic probing of surface acoustic transients

“…Using the transient grating geometry [6][7][8][9], we were able to demonstrate frequency tunability from 1 to ≈6 GHz. Here we demonstrate the broader utility of the TG technique for generating additional planar elastic waves, beyond Rayleigh SAW, which also drive magnetization precession.…”

“…As we had shown previously [7], applying a magnetic field − → H ext in the plane of the sample provides the coupling between the elastic field at frequency v ac / and the ferromagnetic resonance of the film at frequency…”

“…Such an experimental scheme is known to be sensitive to the underlying elastic waves and their associated structural distortions. From the correspondence between the two detection schemes, we are able to fit a single linear relationship (with zero intercept) providing the following mode assignments and their respective velocities: The lower branch propagates at 3120 ± 20 m/s, which we assign as the Rayleigh surface acoustic wave, the same excitation witnessed on MgO substrates [7]. In the long wavelength limit ( >1 μm), the propagation velocity of the Rayleigh SAW in the Ni/substrate heterostructure is dictated by the substrate elastic constants due to the finite penetration depth (≈ h) of the elastic wave.…”

Resonant driving of magnetization precession in a ferromagnetic layer by coherent monochromatic phonons

“…The typical frequencies f M of the magnetic resonances [e.g., the ferromagnetic resonance (FMR) in ferromagnetic and ferrimagnetic materials] are in the GHz and sub-THz frequency ranges. The traditional methods to scan magnetic excitations at these frequencies use microwaves, but due to the requirement of massive microwave resonators providing long wavelength radiation, they cannot provide high-speed control of magnetization locally on the nanoscale.Among various emerging techniques in nanomagnetism, the application of stress to magnetostrictive ferromagnetic layers has been shown to be an effective, low-power method for controlling magnetization: Applying in-plane stress in stationary experiments enables irreversible switching of the magnetization vector [10]; the injection of picosecond strain pulses induces free precession of the magnetization [11]; excitation of quantized elastic waves in a membrane enables driving of the magnetization at GHz phonon frequencies [12]; and surface acoustic waves can be used to control the magnetic dynamics in ferromagnetic nanostructures [13][14][15]. In the present Rapid Communication, we examine the interaction of a high-frequency (10−40 GHz) magnetic resonance in a magnetostrictive ferromagnetic film with an elastic harmonic excitation in the form of a localized phonon mode, and demonstrate how this interaction becomes significantly stronger at resonance conditions.…”