Large Exotic Spin Torques in Antiferromagnetic Iron Rhodium

TL;DR

This paper reports the discovery of large, temperature-dependent exotic spin torques in antiferromagnetic iron rhodium, driven by magnetic ordering, with potential implications for spintronic technologies.

Contribution

It provides experimental measurements and theoretical analysis of exotic spin torques in iron rhodium, highlighting their large magnitude and temperature dependence.

Findings

Spin torque efficiency of 330% at 170 K

Spin torque efficiency of 91% at room temperature

Exotic spin torques are strongly temperature-dependent

Abstract

Spin torque is a promising tool for driving magnetization dynamics for novel computing technologies. These torques can be easily produced by spin-orbit effects, but for most conventional spin source materials, a high degree of crystal symmetry limits the geometry of the spin torques produced. Magnetic ordering is one way to reduce the symmetry of a material and allow exotic torques, and antiferromagnets are particularly promising because they are robust against external fields. We present spin torque ferromagnetic resonance measurements and second harmonic Hall measurements characterizing the spin torques in antiferromagnetic iron rhodium alloy. We report extremely large, strongly temperature-dependent exotic spin torques with a geometry apparently defined by the magnetic ordering direction. We find the spin torque efficiency of iron rhodium to be (330$\pm$150) % at 170 K and (91$\pm$32) % at room temperature. We support our conclusions with theoretical calculations showing how the antiferromagnetic ordering in iron rhodium gives rise to such exotic torques.