On February 6th at 15:00, we have the pleasure to welcome Richard Schlitz from Technische Universität Dresden (Germany). He will give us a seminar at CEA/SPINTEC (*) Bat 1005, room 445, entitled :
Spin Hall magnetoresistance in disordered magnetic insulator/metal heterostructures
The spin Hall magnetoresistance (SMR) can be used as powerful tool to investigate the magnetic state of magnetically ordered insulators (MI). The SMR is observed in heterostructures of a MI and a (spin Hall active) metal. Here, the metal layer acts as a probe for pure spin currents flowing into the magnetic insulator. From the dependence of the metal resistance on magnetic field strength and direction, the magnetic state of the insulator can be inferred. In these MIs, having a ferro-, ferri- or antiferromagnetic state, the metal spins were found to couple to the sublattice magnetizations. However, insulators with a disordered spin system, e.g. paramagnets, have not been investigated in detail.
In this talk I will address the SMR in systems without long range magnetic order. Two possible interaction schemes will be proposed, where the metal spins either couple to the individual spins of the disordered magnet or to the total net magnetic moment. The expected response will be compared to measurements on bilayers of Pt and fully disordered films of yttrium iron garnet. Additionally, results on the SMR in antiferromagnetic insulator/Pt heterostructures above the Néel temperature will be presented. Here, an unexpectedly large signal with the symmetry of the SMR is observed. I will compare the data critically to our the model introduced above for explaining the SMR in disordered systems. Finally, I will conclude with a short overview of additional effects giving rise to signals with the same symmetry as the SMR and discuss their possible contribution to the signals we observe in our material systems.
(*) Persons who do not have a CEA badge must request an entry authorization sufficiently in advance, before November 21th at firstname.lastname@example.org