Impact of current paths on measurement of tunneling magnetoresistance and spin torque critical current densities in GaMnAs-based magnetic tunnel junctions

TL;DR

This paper investigates how current paths affect the measurement of tunneling magnetoresistance and spin torque critical current densities in GaMnAs-based magnetic tunnel junctions, highlighting potential inaccuracies caused by in-plane current shunting.

Contribution

It demonstrates that in-plane current paths can distort measurements of TMR ratios and critical current densities in GaMnAs MTJs, emphasizing the need for careful interpretation of magnetotransport data.

Findings

In-plane current shunting affects perpendicular-to-plane measurements.

Simplified in-plane measurements can estimate TMR ratios.

Inaccuracies in resistance and current density determinations occur due to current paths.

Abstract

GaMnAs-based magnetic tunnel junction (MTJ) devices are characterized by in-plane and perpendicular-toplane magnetotransport at low temperatures. Perpendicular-to-plane transport reveals the typical tunneling magnetotransport (TMR) signal. Interestingly, a similar TMR signature is observed in the in-plane transport signal. Here, low-ohmic shunting of the MTJ by the top contact results in significant perpendicular-to-plane current paths. This effect allows the determination of TMR ratios of MTJs based on a simplified in-plane measurement. However, the same effect can lead to an inaccurate determination of resistance area products and spin torque critical current densities from perpendicular-to-plane magnetotransport experiments on MTJ pillar structures.