Quantifying power flow processes mediated by spin currents

TL;DR

This paper experimentally investigates the power transfer process mediated by spin currents in ferromagnetic/non-magnetic bilayers, quantifying efficiency and identifying key factors affecting energy transfer in spintronic devices.

Contribution

It provides the first detailed experimental quantification of spin current-mediated power transfer efficiency and identifies main factors limiting this efficiency.

Findings

Maximum transfer efficiency of 4.2×10^(-8) under 160mW microwave power

Efficiency is reduced by low resistivity of NM layer and interface loss

Operando measurement of microwave absorption and EMF output in spin pumping

Abstract

The power flow process mediated by spin current in the bilayer device consisting of ferromagnetic metal (FM) and non-magnetic metal (NM) layers is examined by realizing experimental evaluations for each process from the microwave absorption to electromotive force (EMF) output. The absorption power by ferromagnetic resonance (FMR) of the thin FM layer during the EMF output is directly measured in operando using an antenna probe system. The transfer efficiency of the absorption power into the NM layer by spin pumping is estimated from strict linewidth evaluation of EMF spectra. The maximum transfer efficiency of the spin pumping power to the external load via the inverse spin Hall effect is determined to be 4.2X10^(-8) under 160mW microwave irradiation using an analysis model assuming a parallel circuit. The main factors reducing the efficiency are found to be low resistivity of the NM layer and the interface loss. These quantifications are important as a first step to consider the efficient transfer of spin energy mediated by spin currents.