Large Spin Hall Magnetoresistance in Antiferromagnetic α−Fe2O3/Pt Heterostructures

We investigate the spin Hall magnetoresistance (SMR) at room temperature in thin-film heterostructures of antiferromagnetic insulating (0001)-oriented $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}$ (hematite) and $\mathrm{Pt}$. We measure their longitudinal and transverse resistivities while rotating an applied magnetic field of up to 17 T in three orthogonal planes. For out-of-plane magnetotransport measurements, we find indications for a multidomain antiferromagnetic configuration whenever the field is aligned along the film normal. For in-plane field rotations, we clearly observe a sinusoidal resistivity oscillation characteristic for the SMR due to a coherent rotation of the N\'eel vector. The maximum SMR amplitude of $0.25\mathrm{%}$ is, surprisingly, twice as high as for prototypical ferrimagnetic ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}/\mathrm{Pt}$ heterostructures. The SMR effect saturates at much smaller magnetic fields than in comparable antiferromagnets, making the $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Fe}}_{2}{\mathrm{O}}_{3}/\mathrm{Pt}$ system particularly interesting for room-temperature antiferromagnetic spintronic applications.