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We unravel the origin of current-induced magnetic switching of insulating antiferromagnet/heavy metal systems. We utilize concurrent transport and magneto-optical measurements to image the switching of antiferromagnetic domains in specially engineered devices of NiO/Pt bilayers. Different electrical pulsing and device geometries reveal different final states of the switching with respect to the current direction. We can explain these through simulations of the temperature induced strain and we identify the thermomagnetoelastic switching mechanism combined with thermal excitations as the origin, in which the final state is defined by the strain distributions and heat is required to switch the antiferromagnetic domains. We show that such a potentially very versatile non-contact mechanism can explain the previously reported contradicting observations of the switching final state, which were attributed to spin-orbit torque mechanisms.

Spintronics seeks to functionalize antiferromagnetic materials to develop memory and logic devices operating at terahertz speed and robust against external magnetic field perturbations. To be useful, such functionality needs to be developed in thin film devices. The key functionality of long-distance spin-transport has, however, so far only been reported in bulk single crystal antiferromagnets, while in thin films, transport has so far been limited to a few nanometers. In this work, we electrically achieve a long-distance propagation of spin-information in thin films of the insulating antiferromagnet hematite. Through transport and magnetic imaging, we demonstrate a strong correlation between the efficiency of the transport of magnons, which carry spin-information, and the magnetic domain structure of the films. In thin films with large domains, magnons propagate over micrometer distances whilst they attenuate over much shorter distances in multidomain thin films. The governing factor of the attenuation is related to scattering at domain walls, and we demonstrate that we can reduce this through training by field cyclings. For the appropriate crystalline orientation of the films, spin-transport is achieved in zero applied field across micrometers, as required for integration with devices.