Spin pumping with coherent elastic waves

TL;DR

This paper demonstrates that resonant coupling of phonons and magnons via surface acoustic waves can generate spin currents at room temperature, introducing acoustic spin pumping as a new resonant mechanism for spin current generation.

Contribution

It presents the first experimental evidence of acoustic spin pumping using coherent elastic waves in a ferromagnetic/normal metal bilayer at room temperature.

Findings

Spin current is generated only during resonant elastic excitation.

Inverse spin Hall voltage correlates with the presence of surface acoustic waves.

Acoustic spin pumping acts as a resonant analogue to the spin Seebeck effect.

Abstract

We show that the resonant coupling of phonons and magnons can be exploited to generate spin currents at room temperature. Surface acoustic wave (SAW) pulses with a frequency of 1.55 GHz and duration of 300 ns provide coherent elastic waves in a ferromagnetic thin film/normal metal (Co/Pt) bilayer. We use the inverse spin Hall voltage in the Pt as a measure for the spin current and record its evolution as a function of time and external magnetic field magnitude and orientation. Our experiments show that a spin current is generated in the exclusive presence of a resonant elastic excitation. This establishes acoustic spin pumping as a resonant analogue to the spin Seebeck effect.