Efficient Spin Transport through Native Oxides of Nickel and Permalloy with Platinum and Gold Overlayers
Publication Date
5-2-2016
Document Type
Article
Organizational Units
College of Natual Science and Mathematics, Physics and Astronomy
Keywords
Ferromagnetic resonance, Platinum overlayer, Gold overlayer, Nickel, Inverse spin Hall effect
Abstract
We present measurements of spin pumping detected by the inverse spin Hall effect voltage and ferromagnetic resonance spectroscopy in a series of metallic ferromagnet/normal metal thin film stacks. We compare heterostructures grown in situ to those where either a magnetic or nonmagnetic oxide is introduced between the two metals. The heterostructures, either nickel with a platinum overlayer (Ni/Pt) or the nickel-iron alloy permalloy (Py) with a gold overlayer (Py/Au), were also characterized in detail using grazing-incidence x-ray reflectivity, Auger electron spectroscopy, and both SQUID and alternating-gradient magnetometry. We verify the presence of oxide layers, characterize layer thickness, composition, and roughness, and probe saturation magnetization, coercivity, and anisotropy. The results show that while the presence of a nonmagnetic oxide at the interface suppresses spin transport from the ferromagnet to the nonmagnetic metal, a thin magnetic oxide (here the native oxide formed on both Py and Ni) somewhat enhances the product of the spin-mixing conductance and the spin Hall angle. We also observe clear evidence of an out-of-plane component of magnetic anisotropy in Ni/Pt samples that is enhanced in the presence of the native oxide, resulting in perpendicular exchange bias. Finally, the dc inverse spin Hall voltages generated at ferromagnetic resonance in our Py/Au samples are large, and suggest values for the spin Hall angle in gold of 0.04<αSH<0.22, in line with the highest values reported for Au. This is interpreted as resulting from Fe impurities. We present indirect evidence that the Au films described here indeed have significant impurity levels.
Publication Statement
Copyright held by author or publisher. User is responsible for all copyright compliance.
Recommended Citation
Zink, B. L, Manno, M, O'Brien, L, Lotze, J, Weiler, M, Bassett, D, Mason, S. J, Goennenwein, S. T. B, Johnson, M, and Leighton, C. "Efficient Spin Transport through Native Oxides of Nickel and Permalloy with Platinum and Gold Overlayers." Physical Review. B 93.18 (2016): Physical Review. B, 2016-05, Vol.93 (18). Web. doi: 10.1103/physrevb.93.184401.