Spin Torque Generated by the Spin Hall Effect in Ferromagnets

Ferromagnetic materials exhibit the anomalous Hall effect, the generation of a transverse charge current due to spin-orbit coupling. The anomalous Hall effect is closely related to the spin Hall effect, and hence this transverse charge current is expected to be accompanied by a strong transverse spin current, whose direction can be manipulated by rotating the magnetic moment. We measure the torque from this spin current generated by Gd-doped Fe and acting on an in-plane magnetized free layer. We use the harmonic measurement technique, applying a current to an in-plane pinned ferromagnet/spacer/in-plane free ferromagnet stack and measuring the second harmonic Hall voltage. We report the angular dependence of the spin torque for a variety of initial exchange bias directions, and as the spin torque changes with an external magnetic field.