Nonlocal magnon spin transport in yttrium iron garnet with tantalum and platinum spin injection/detection electrodes

TL;DR

This study investigates magnon spin transport in yttrium iron garnet (YIG) using platinum and tantalum electrodes, revealing how interface properties and spin Hall angles influence magnon transport efficiency.

Contribution

It provides a comparative analysis of magnon spin transport with different heavy metal electrodes and introduces a circuit model to quantify interface effects on magnon relaxation.

Findings

Magnon relaxation length is approximately 10 micrometers for both Pt and Ta devices.

Interface properties significantly affect magnon spin transport, with Ta showing reduced spin mixing conductance.

The circuit model accurately predicts the dependence of nonlocal signals on injector-detector distance.

Abstract

We study the magnon spin transport in the magnetic insulator yttrium iron garnet (YIG) in a nonlocal experiment and compare the magnon spin excitation and detection for the heavy metal paramagnetic electrodes platinum (Pt|YIG|Pt) and tantalum (Ta|YIG|Ta). The electrical injection and detection processes rely on the (inverse) spin Hall effect in the heavy metals and the conversion between the electron spin and magnon spin at the heavy metal|YIG interface. Pt and Ta possess opposite signs of the spin Hall angle. Furthermore, their heterostructures with YIG have different interface properties, i.e. spin mixing conductances. By varying the distance between injector and detector, the magnon spin transport is studied. Using a circuit model based on the diffusion-relaxation transport theory, a similar magnon relaxation length of ~ 10 \mu m was extracted from both Pt and Ta devices. By changing the injector and detector material from Pt to Ta, the influence of interface properties on the magnon spin transport has been observed. For Ta devices on YIG the spin mixing conductance is reduced compared with Pt devices, which is quantitatively consistent when comparing the dependence of the nonlocal signal on the injector-detector distance with the prediction from the circuit model.