Spin Transport in Insulating Ferri- and Antiferromagnets
Institute of Physics, Johannes Gutenberg-University Mainz, Germany
We probe spin transport in ferrimagnets  and insulating antiferromagnets, such as NiO by thermal spin currents resulting from the spin Seebeck effect and by spin pumping measurements and we find short (few nm) spin diffusion lengths . We use a magnonic spin valve device made of collinear magnetic yttrium iron garnet (YIG)/CoO/Co multilayers . By means of microwaves and external magnetic fields YIG is brought into ferromagnetic resonance, resulting in a pure spin current propagating through the sample stack and finally being detected in the Co layer via the inverse spin Hall effect. For parallel and antiparallel alignment of the ferromagnetic layers, we observe a very different amplitude of the magnonic spin current transmitted across the AFM with a spin valve effect amplitude of 120% . Furthermore, by varying the antiferromagnetic layer thickness, we can determine the spin current attenuation length in NiO and CoO to a few nm also for this case. Finally, we carry out non-local spin transport experiments on collinear antiferromagnets. We find that by tuning the spin structure we can realize spin transport over tens of micrometer distances  and switching in antiferromagnets can be obtained by spin-orbit torques .
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 J. Cramer et al., Nature Comm. 9, 1089 (2018)
 R. Lebrun et al., Nature 561, 222 (2018).
 S. Bodnar et al., Nature Comm. 9, 348 (2018)
Mathias Kläui received PhD in Physics at the University of Cambridge, Great Britain in 2003. From 2003 to 2008, he was a postdoctoral researcher at the IBM Zurich Research Laboratory, Switzerland, and then a senior scientist at the Universität Konstanz, Germany. Since 2011, he is a full Professor at the Johannes Gutenberg-Universität Mainz, Germany. Prof. Kläui has published over 230 reviewed publications (h-factor 42). He is a Senior Member of the IEEE, Director of the Graduate School of Excellence: Materials Science in Mainz. He is the recipient of the Nicholas Kurti Prize for Research in Physical Sciences and Distinguished Clerk Maxwell Scholar of the Cavendish Laboratory, Cambridge.
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