Unconventional Field-Like Spin-Torques in CrPt$_3$

TL;DR

This study investigates unconventional spin torques in CrPt$_3$ films with different magnetic orderings, revealing direction-dependent field-like torques originating from interface effects and spin scattering, advancing understanding of spin-orbit phenomena in topological materials.

Contribution

It demonstrates the existence of direction-dependent unconventional spin torques in CrPt$_3$, linking magnetic ordering and interface effects to torque generation.

Findings

Unconventional field-like torque observed in CrPt$_3$ films.

Torque sign depends on current direction relative to crystal axes.

Interface spin scattering contributes to the torque mechanism.

Abstract

The topological semimetal CrPt$_3$ has potential for generating unconventional spin torques due to its ferrimagnetic ordering, topological band structure, and high anomalous Hall effect. CrPt$_3$ exhibits ferrimagnetic behavior only in its chemically ordered phase and is paramagnetic in its chemically disordered phase. By controlling the growth and annealing temperatures, epitaxial films of both chemically ordered and disordered phases of CrPt$_3$ are prepared allowing us to investigate the role of magnetic ordering on unconventional torque generation. We use angle dependent spin-torque ferromagnetic resonance and second harmonic Hall measurements to probe the spin torques generated from epitaxial CrPt$_3$ in CrPt$_3$/Cu/Ni$_{81}$Fe$_{19}$ heterostructures. With current applied along specific directions with respect to the crystal order we reveal unconventional spin torques in both ordered and disordered films. When current flows parallel to the $[1\overline{1}1]$ and $[\overline{1}11]$ directions we observe an unconventional field-like torque that is opposite in sign for the two directions. Our calculations reveal that this unconventional torque originates from an indirect nonlocal spin-orbit torque due to spin scattering at the CrPt$_3$/Cu interface, in addition to symmetry breaking at this interface.