Description:

Metallic antiferromagnets have generated a wide range of interest recently, since they can exhibit a complex interplay between charge transport and magnetic structure [1,2].  In this presentation I will highlight some of our own recent work in that respect.  First I will discuss, how magnetic field induced changes of the antiferromagnetic magnetic structure can result in interfacial unidirectional magnetoresistance [3].  Then subsequently, I will focus on spin Hall effects in metallic antiferromagnets.  We showed that CuAu-I-type metallic antiferro­magnets (PtMn, IrMn, PdMn, and FeMn) have significant spin Hall effects, which in the case of PtMn become comparable to the ubiquitously used Pt [4].  The spin Hall angles increase for the alloys with heavier element; consistent with first-principle calculations of the spin Hall conductivities based on intrinsic spin Hall effects.  Furthermore, the calculations suggest pronounced anisotropies of the spin Hall conductivities, which we verified using epitaxially grown antiferromagnetic films [5].  One peculiar aspect of antiferromagnets is that the antiferromagnetic spin structures can give rise to additional symmetry breaking, which in turn enables the generation of spin currents with novel geometries.  Towards this end, we detected the magnetic spin Hall effects in IrMn3 via the spin-orbit torques exerted on an adjacent ferromagnetic layer [6].  Furthermore, we explored spin-orbit torques in FeRh and discovered that in the antiferromagnetic state FeRh exhibits unusually strong spin-orbit torques with exotic symmetries [7].  Lastly, I will discuss, how the novel spin-orbit torques from antiferromagnets may in turn be used for driving new magnetization dynamics [8].

This work was supported as part pf the Quantum Materials for Energy Efficient Neuromorphic Computing, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Materials Sciences through Award # DE-SC0019273, the National Science Foundation through the University of Illinois at Urbana-Champaign Materials Research Science and Engineering Center under Grant No. DMR-1720633 and was, in part, carried out in the Materials Research Laboratory Central Research Facilities, University of Illinois.

 Axel Hoffmann, Professor, Materials Science and Engineering, University of Illinois, Urbana-Champaign

Host: John Ketterson