Antiferromagnetic Insulatronics: Spintronics without Magnetic Fields and Moving Electrons

With information technology consuming a sizeable part of the total energy, “GreenIT” information storage and computing technology will have a major impact to address societal challenges. Traditionally, magnetism has been the prime approach to non-volatile data storage and spintronics devices for memory and sensing have been realized. However so far, spintronics is linked inextricably to ferromagnets in metals entailing major disadvantages, such as ohmic losses during operation and unwanted interactions due to stray fields. A possible novel approach is to use antiferomagnets. While known for a long time, antiferromagnetically ordered systems have previously been considered, as expressed by Louis Néel in his Nobel Prize Lecture, to be “interesting but useless”. However, since antiferromagnets potentially promises faster operation, enhanced stability with respect to interfering magnetic fields and higher integration due to the absence of dipolar coupling, they could potentially become a game changer for new spintronic devices. I will introduce the key operations of reading and writing the antiferromagnetic order to store and retrieve information and how to transport information using low loss spin currents. Reading can be achieved in metallic as well as insulating antiferromagnetic heterostructures using special magnetoresistance effects and efficient switching of antiferromagnets has been demonstrated by spin orbit torques. Spin currents have been shown to carry information with unprecedented efficiency in the insulating antiferromagnet hematite, the main component of rust showing that very common materials can be used in unexpected ways! Key publications: R. Lebrun et al.; Tunable long-distance spin transport in a crystalline antiferromagnetic iron oxide; Nature 561, 222 (2018) S. Bodnar et al., Writing and reading antiferromagnetic Mn2Au by Néel spin-orbit torques and large anisotropic magnetoresistance; Nature Communications 9, 348 (2018) J. Cramer et al., Magnon detection using a ferroic collinear multilayer spin valve; Nature Communications 9, 1089 (2018) M. Kläui et al., Exploiting Coherence in Nonlinear Spin-Superfluid Transport, Phys. Rev. Lett. 119, 187705 (2017) S. Geprägs et al., Origin of the spin Seebeck effect in compensated ferrimagnets; Nature Communications 7, 10452 (2016)