We study the flow of a pure spin current through zinc oxide by measuring the spin Hall magnetoresistance (SMR) in thin film trilayer samples consisting of bismuth-substituted yttrium iron garnet (Bi:YIG), gallium-doped zinc oxide (Ga:ZnO), and platinum. We investigate the dependence of the SMR magnitude on the thickness of the Ga:ZnO interlayer and compare to a Bi:YIG/Pt bilayer. We find that the SMR magnitude is reduced by almost one order of magnitude upon inserting a Ga:ZnO interlayer and continuously decreases with increasing interlayer thickness. Nevertheless, the SMR stays finite even for a thick Ga:ZnO interlayer. These results show that a pure spin current indeed can propagate through a several nm-thick degenerately doped zinc oxide layer. We also observe differences in both the temperature and the field dependence of the SMR when comparing tri- and bilayers. Finally, we compare our data to the predictions of a model based on spin diffusion. This shows that interface resistances play a crucial role for the SMR magnitude in these trilayer structures.
Pure spin current transport in gallium doped zinc oxide
Matthias Althammer, Joynarayan Mukherjee, Stephan Geprägs, Sebastian T. B. Goennenwein, Matthias Opel, M. S. Ramachandra Rao, Rudolf Gross; Pure spin current transport in gallium doped zinc oxide. Appl. Phys. Lett. 30 January 2017; 110 (5): 052403. https://doi.org/10.1063/1.4975372
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