Inplane spin orbit torque magnetization switching and its detection using the spin rectification effect at sub-GHz frequencies

TL;DR

This paper demonstrates a sensitive method for detecting in-plane magnetization reversal in a permalloy/platinum bilayer using spin rectification at sub-GHz frequencies, enabling simple device integration.

Contribution

It introduces a novel detection technique for in-plane SOT switching using spin rectification at low frequencies, applicable to small-scale devices.

Findings

Detection of magnetization reversal via discrete DC voltages.

Threshold current density for switching is 10-20 MA/cm^2.

Signal magnitude is comparable or larger than standard ST-FMR signals.

Abstract

Inplane magnetization reversal of a permalloy/platinum bilayer was detected using the spin rectification effect. Using a sub GHz microwave frequency to excite spin torque ferromagnetic resonance (ST FMR) in the bilayer induces two discrete DC voltages around an external static magnetic field of 0 mT. These discrete voltages depend on the magnetization directions of the permalloy and enable detection of the inplane magnetization reversal. The threshold current density for the magnetization reversal is from 10 to 20 MA/cm^2, the same order as for known spin orbit torque (SOT) switching with in-plane magnetization materials. The magnitude of the signal is the same or larger than that of the typical ST FMR signal; that is, detection of magnetization switching is highly sensitive in spite of deviation from the optimal ST-FMR condition. The proposed method is applicable to a simple device structure even for a small ferromagnetic electrode with a width of 100 nm.