Spin-transfer torques for domain walls in antiferromagnetically coupled ferrimagnets

TL;DR

This paper presents experimental evidence that spin-transfer torque can effectively drive domain walls in antiferromagnetically-coupled ferrimagnets, revealing a larger non-adiabaticity parameter than damping, which enables faster antiferromagnetic device operation.

Contribution

It provides the first experimental demonstration of STT effects on domain walls in antiferromagnetically-coupled ferrimagnets, challenging existing ferromagnetic-based models.

Findings

Non-adiabatic STT acts like a staggered magnetic field.

The non-adiabaticity parameter {eta} exceeds the Gilbert damping {\u03b1}.

Fast current-induced domain wall motion observed.

Abstract

Antiferromagnetic materials are outstanding candidates for next generation spintronic applications, because their ultrafast spin dynamics makes it possible to realize several orders of magnitude higher-speed devices than conventional ferromagnetic materials1. Though spin-transfer torque (STT) is a key for electrical control of spins as successfully demonstrated in ferromagnetic spintronics, experimental understanding of STT in antiferromagnets has been still lacking despite a number of pertinent theoretical studies2-5. Here, we report experimental results on the effects of STT on domain-wall (DW) motion in antiferromagnetically-coupled ferrimagnets. We find that non-adiabatic STT acts like a staggered magnetic field and thus can drive DWs effectively. Moreover, the non-adiabaticity parameter {\beta} of STT is found to be significantly larger than the Gilbert damping parameter {\alpha}, challenging our conventional understanding of the non-adiabatic STT based on ferromagnets as well as leading to fast current-induced antiferromagnetic DW motion. Our study will lead to further vigorous exploration of STT for antiferromagnetic spin textures for fundamental physics on spin-charge interaction as wells for efficient electrical control of antiferromagnetic devices.