Suppressing Electrical Switching of Antiferromagnets with High Magnetic Fields

Abstract

Antiferromagnetic (AF) spintronics received an enormous impulse after the first demonstrations of electrical switching of the AF order [1]. However, a lot of these observations can equally well be explained by non-magnetic, parasitic effects caused by the same electrical current pulses that are intended to manipulate the magnetic state of the AF [2].While it is possible to distinguish between magnetic and non-magnetic effects using imaging techniques that can resolve the AF order [3], these techniques are usually very complex. Moreover, since they require access to the AF layer, they are not suitable for systems where the AF is buried beneath other layers. Our approach is to distinguish between the magnetic and non-magnetic effects by suppressing the magnetic effects using high magnetic fields.In this contribution, we study the high magnetic field behavior of the electrical switching of thin-film AFs NiO and CoO, using the devices shown in Fig. 1. We perform switching experiments in magnetic fields up to 16 Tesla (Fig. 2). The measurements show that these high magnetic fields indeed suppress the current-induced switching of the AF order, whereas the thermal effects remain unaffected. Hence, this technique allows to irrefutably separate the magnetic and non-magnetic effects. These results are corroborated by a model accounting for the multi-domain character of the AF.Finally, the experiments with CoO yield an unexpected dependence of the magnetic configuration on the direction of the high magnetic fields. This indicates an unexpectedly complex magnetic anisotropy in CoO that depends on the magnetic field strength and orientation, most likely due to unquenched orbital momentum.These results both demonstrate that combining electrical methods with strong magnetic fields can be a valuable tool for AF spintronics, and give invaluable insight into the interplay of spin-Hall magnetoresistance and thermal effects as well as the domain structure and complex anisotropy of thin-film antiferromagnets.  Fig. 1: Micrograph of the device used for the experiments.  Fig. 2: Switching amplitude as a function of magnetic field. The lines are calculated with the model; the pie charts represent the modeled domain distribution.