Magnon Valve Effect Between Two Magnetic Insulators

TL;DR

This paper demonstrates a magnon valve effect using two ferromagnetic insulators separated by a nonmagnetic layer, where thermal gradients control magnon currents via spin Seebeck effect, revealing new spintronic device possibilities.

Contribution

It introduces the concept of a magnon valve with magnetic insulators and nonmagnetic spacers, expanding beyond traditional spin valves with conduction electrons.

Findings

Magnon current depends on the relative magnetization orientation.

The magnon valve ratio follows a power-law temperature dependence.

The effect demonstrates angular momentum transfer between magnons and electrons.

Abstract

The key physics of the spin valve involves spin-polarized conduction electrons propagating between two magnetic layers such that the device conductance is controlled by the relative magnetization orientation of two magnetic layers. Here, we report the effect of a magnon valve which is made of two ferromagnetic insulators (YIG) separated by a nonmagnetic spacer layer (Au). When a thermal gradient is applied perpendicular to the layers, the inverse spin Hall voltage output detected by a Pt bar placed on top of the magnon valve depends on the relative orientation of the magnetization of two YIG layers, indicating the magnon current induced by spin Seebeck effect at one layer affects the magnon current in the other layer separated by Au. We interpret the magnon valve effect by the angular momentum conversion and propagation between magnons in two YIG layers and conduction electrons in the Au layer. The temperature dependence of magnon valve ratio shows approximately a power law, supporting the above magnon-electron spin conversion mechanism. This work opens a new class of valve structures beyond the conventional spin valves.