Interface control of the magnetic chirality in TaN|CoFeB|MgO heterosctructures

TL;DR

This study demonstrates that the magnetic chirality in TaN|CoFeB|MgO heterostructures can be controlled by modifying the non-magnetic layer, which reverses the Dzyaloshinskii-Moriya interaction and affects domain wall motion.

Contribution

It reveals that doping the Ta layer with nitrogen reverses the DMI sign, providing a new method to control magnetic chirality in heterostructures.

Findings

DMI sign is reversed by nitrogen doping in Ta layers.

The spin Hall angle remains the same despite doping.

DMI sign determines domain wall motion direction.

Abstract

Recent advances in the understanding of spin orbital effects in ultrathin magnetic heterostructures have opened new paradigms to control magnetic moments electrically. The Dzyaloshinskii-Moriya interaction (DMI) is said to play a key role in forming a Neel-type domain wall that can be driven by the spin Hall torque, a torque resulting from the spin current generated in a neighboring non-magnetic layer via the spin Hall effect. Here we show that the sign of the DMI, which determines the direction to which a domain wall moves with current, can be changed by modifying the adjacent non-magnetic layer. We find that the sense of rotation of a domain wall spiral is reversed when the Ta underlayer is doped with nitrogen in Ta|CoFeB|MgO heterostructures. The spin Hall angle of the Ta and nitrogen doped Ta underlayers carry the same sign, suggesting that the sign of the DMI is defined at the interface. Depending on the sense of rotation, spin transfer torque and spin Hall torque can either compete or assist each other, thus influencing the efficiency of moving domain walls with current.