Acoustic spin pumping
Context of project
Spin pumping is a mechanism in which a flow of angular momentum or spin current is generated. One of the most common methods to pump spin current is via ferromagnetic resonance (FMR), in which the magnetization of a ferromagnet is driven into precession in resonant condition. If a non-magnetic metal is attached to the ferromagnet the FMR pumps spins into the non-magnetic metal . The FMR is usually driven by microwave photons generated in a coplanar waveguide. An alternative is to drive the FMR by phonons which couple to the magnetization via the magneto-elastic effect, this is known as acoustic FMR and the consequent pumping of spins as acoustic spin pumping [2, 3].
In this project we excite acoustic FMR by coupling surface acoustic waves (SAWs) at GHz frequencies with ferromagnetic layers grown on top of a piezoelectric substrate. The generated spin current is detected and studied by the inverse Edelstein effect induced at interfaces with Rashba spin orbit coupling or the inverse spin Hall effect in heavy metals.
Spin pumping reference:
Acoustic ferromagnetic resonance and spin pumping references:
Based on acoustic spin pumping experiments we have demonstrated efficient spin to charge conversion, comparable to that of more standard microwave photon excited ferromagnetic resonance (FMR). In our experiments we generate surface acoustic waves (SAW) in a piezoelectric substrate (LiNbO3) and couple the SAW to a Ni layer which injects spin current into a interface with spin orbit coupling which allow us to convert the spin current to voltage by the "inverse Edelstein effect".
Inverse Edelstein effect induced by magnon-phonon coupling
M. Xu, J. Puebla, F. Auvray, B. Rana, K. Kondou, Y. Otani
Physical Review B 97 (18), 180301 (2018)
Personal contribution: Project leader (corresponding author), proposed project, supervised experiments and data analysis, writing of manuscript
Leave a Reply.