Observation of spin-splitter torque in collinear antiferromagnetic RuO$_2$

TL;DR

This study demonstrates the generation of spin-splitter torque in collinear antiferromagnetic RuO₂, enabling field-free magnetization switching at room temperature, advancing antiferromagnetic spin-orbitronics for spintronic device applications.

Contribution

It provides experimental evidence of spin-splitter torque in RuO₂ and explores its dependence on crystal orientation and Néel vector, revealing new mechanisms for antiferromagnetic spin current manipulation.

Findings

All spin current polarizations depend on the Néel vector orientation.

Only y-polarized spin current is present in RuO₂(100) and (001), independent of Néel vector.

Field-free switching of perpendicular magnetized ferromagnet achieved at room temperature.

Abstract

The spin-splitter effect is theoretically predicted to generate an unconventional spin current with $\mathit{x}$- and $\mathit{z}$- spin polarization via the spin-split band in antiferromagnets. The generated torque, namely spin-splitter torque, is effective for the manipulation of magnetization in an adjacent magnetic layer without an external magnetic field for spintronic devices such as MRAM. Here, we study the generation of torque in collinear antiferromagnetic RuO$_2$ with (100), (101), and (001) crystal planes. Next we find all $\mathit{x}$-, $\mathit{y}$-, and $\mathit{z}$-polarized spin currents depending on the N\'{e}el vector direction in RuO$_2$(101). For RuO$_2$(100) and (001), only $\mathit{y}$-polarized spin current was present, which is independent of the N\'{e}el vector. Using the $\mathit{z}$-polarized spin currents, we demonstrate field-free switching of the perpendicular magnetized ferromagnet at room temperature. The spin-splitter torque generated from RuO$_2$ is verified to be useful for the switching phenomenon and paves the way for a further understanding of the detailed mechanism of the spin-splitter effect and for developing antiferromagnetic spin-orbitronics.