Suppression of spin-pumping by a MgO tunnel-barrier

TL;DR

This study investigates how an MgO tunnel barrier affects spin-pumping efficiency at ferromagnet/normal metal interfaces, revealing suppression contrary to some previous reports suggesting enhancement.

Contribution

It provides direct electrical measurements showing that an MgO tunnel barrier suppresses spin-pumping, challenging prior assumptions about interface effects on spin mixing conductance.

Findings

Spin-pumping is suppressed by the MgO tunnel barrier.

Inverse spin Hall effect detects reduced spin currents with the barrier.

Contradicts previous studies suggesting enhancement of spin mixing conductance.

Abstract

Spin-pumping generates pure spin currents in normal metals at the ferromagnet (F)/normal metal (N) interface. The efficiency of spin-pumping is given by the spin mixing conductance, which depends on N and the F/N interface. We directly study the spin-pumping through an MgO tunnel-barrier using the inverse spin Hall effect, which couples spin and charge currents and provides a direct electrical detection of spin currents in the normal metal. We find that spin-pumping is suppressed by the tunnel-barrier, which is contrary to recent studies that suggest that the spin mixing conductance can be enhanced by a tunnel-barrier inserted at the interface.