Control of spin current by a magnetic YIG substrate in NiFe/Al nonlocal spin valves

TL;DR

This study demonstrates how a magnetic YIG substrate influences spin current transport in NiFe/Al nonlocal spin valves, showing significant spin absorption at the interface and a small modulation of the spin signal with magnetization orientation.

Contribution

It provides the first quantitative measurement of spin-mixing conductance at the Al/YIG interface and explores the impact of YIG on spin transport properties in nonlocal spin valves.

Findings

NLSV signal is 2-3 times lower on YIG than on SiO2.

Effective spin-mixing conductance G↑↓ ≈ 5-8×10^{13} Ω^{-1}m^{-2}.

Small modulation of NLSV signal with YIG magnetization rotation.

Abstract

We study the effect of a magnetic insulator (Yttrium Iron Garnet - YIG) substrate on the spin transport properties of Ni$_{80}$Fe$_{20}$/Al nonlocal spin valve (NLSV) devices. The NLSV signal on the YIG substrate is about 2 to 3 times lower than that on a non magnetic SiO$_2$ substrate, indicating that a significant fraction of the spin-current is absorbed at the Al/YIG interface. By measuring the NLSV signal for varying injector-to-detector distance and using a three dimensional spin-transport model that takes spin current absorption at the Al/YIG interface into account we obtain an effective spin-mixing conductance $G_{\uparrow\downarrow}\simeq 5 - 8\times 10^{13}~\Omega^{-1}$m$^{-2}$. We also observe a small but clear modulation of the NLSV signal when rotating the YIG magnetization direction with respect to the fixed spin polarization of the spin accumulation in the Al. Spin relaxation due to thermal magnons or roughness of the YIG surface may be responsible for the observed small modulation of the NLSV signal.