We report on the determination of the anomalous spin Hall angle in the ferromagnetic metal alloy cobalt-iron (Co25Fe75, CoFe). This is accomplished by measuring the spin injection/detection efficiency in a multiterminal device with nanowires of platinum (Pt) and CoFe deposited onto the magnetic insulator yttrium iron garnet (Y3Fe5O12, YIG). Applying a spin-resistor model to our multiterminal spin transport data, we determine the magnon conductivity in YIG, the spin conductance at the YIG/CoFe interface, and finally the anomalous spin Hall angle of CoFe as a function of its spin diffusion length in a single device. Our experiments clearly reveal a negative anomalous spin Hall angle of the ferromagnetic metal CoFe, but a vanishing ordinary spin Hall angle. This work, therefore, adds new observations to the results reported in Tian et al. [Phys. Rev. B 94, 020403 (2016)] and Das et al. [Phys. Rev. B 96, 220408(R) (2017)] , where the authors found finite contributions of the ordinary spin Hall angle in the ferromagnetic metals Co and Permalloy.
Anomalous spin Hall angle of a metallic ferromagnet determined by a multiterminal spin injection/detection device
T. Wimmer, B. Coester, S. Geprägs, R. Gross, S. T. B. Goennenwein, H. Huebl, M. Althammer; Anomalous spin Hall angle of a metallic ferromagnet determined by a multiterminal spin injection/detection device. Appl. Phys. Lett. 26 August 2019; 115 (9): 092404. https://doi.org/10.1063/1.5101032
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