Probing the Spin Pumping Mechanism: Exchange Coupling with Exponential Decay in Y3Fe5O12/barrier/Pt Heterostructures

TL;DR

This study demonstrates that spin pumping in Y3Fe5O12/Pt heterostructures decays exponentially with barrier thickness, highlighting quantum tunneling and exchange coupling as key mechanisms influencing spin current transfer.

Contribution

It provides direct experimental evidence of exponential decay in spin pumping due to quantum tunneling, emphasizing the role of exchange interaction and barrier properties.

Findings

Exponential decay lengths of 0.16 and 0.23 nm for different oxide barriers.

Thousand-fold decay of spin pumping across insulating barriers.

Quantum tunneling signature confirms exchange coupling's importance.

Abstract

Ferromagnetic resonance driven spin pumping of pure spin currents from a ferromagnet into a nonmagnetic material promises new spin-functional devices with low energy consumption. The mechanism of spin pumping is under intense investigation and it is widely believed that exchange interaction between the ferromagnet and nonmagnetic material is responsible for this phenomenon. We observe a thousand-fold exponential decay of the spin pumping from 20-nm thick Y3Fe5O12 films to platinum across insulating barriers, from which the exponential decay lengths of 0.16 and 0.23 nm are extracted for oxide barriers with band gaps of 4.93 eV and 2.36 eV, respectively. This prototypical signature of quantum tunneling through a barrier underscores the importance of exchange coupling for spin pumping and reveals its dependence on the characteristics of the barrier material.