Giant bulk spin-orbit torque and efficient electrical switching in single ferrimagnetic FeTb layers with strong perpendicular magnetic anisotropy

TL;DR

This paper reports a giant bulk spin-orbit torque in ferrimagnetic FeTb layers with strong perpendicular magnetic anisotropy, enabling efficient electrical switching at low current densities, promising for ultralow-power magnetic devices.

Contribution

It demonstrates a record-high bulk damping-like spin-orbit torque efficiency in amorphous FeTb layers, revealing composition-dependent effects and potential for low-power magnetic switching.

Findings

Record-high spin-orbit torque efficiency of 0.036 nm^-1.

Giant torque enables switching of 10s of nm thick layers.

Torque efficiency varies strongly with composition, even changing sign.

Abstract

Efficient manipulation of antiferromagnetically coupled materials that are integration-friendly and have strong perpendicular magnetic anisotropy (PMA) is of great interest for low-power, fast, dense magnetic storage and computing. Here, we report a distinct, giant bulk damping-like spin-orbit torque in strong-PMA ferrimagnetic Fe100-xTbx single layers that are integration-friendly (composition-uniform, amorphous, sputter-deposited). For sufficiently-thick layers, this bulk torque is constant in the efficiency per unit layer thickness, {\xi}_DL^j/t, with a record-high value of 0.036nm-1, and the dampinglike torque efficiency {\xi}_DL^j achieves very large values for thick layers, up to 300% for 90 nm layers. This giant bulk torque by itself switches tens of nm thick Fe100-xTbx layers that have very strong PMA and high coercivity at current densities as low as a few MA/cm2. Surprisingly, for a given layer thickness, {\xi}_DL^j shows strong composition dependence and becomes negative for composition where the total angular momentum is oriented parallel to the magnetization rather than antiparallel. Our findings of giant bulk spin torque efficiency and intriguing torque-compensation correlation will stimulate study of such unique spin-orbit phenomena in a variety of ferrimagnetic hosts. This work paves a promising avenue for developing ultralow-power, fast, dense ferrimagnetic storage and computing devices.