Determination of the spin Hall angle in single-crystalline Pt films from spin pumping experiments

Abstract

We report on the determination of the spin Hall angle and the identification\nof the role of the interface roughness for the inverse spin Hall effect (ISHE)\nin ultra-clean, defect-reduced epitaxial Pt films. By applying vector network\nanalyzer ferromagnetic resonance spectroscopy to a series of single crystalline\nFe (12 nm) /Pt (t$_\\text{Pt}$) bilayers we determine the real part of the spin\nmixing conductance $(4.4\\:\\pm\\:0.2)\\cdot 10^{19}\\: $m$^{-2}$ and reveal a very\nsmall spin diffusion length in the epitaxial Pt $(1.1\\:\\pm\\:0.1)$ nm film. We\ninvestigate the spin pumping and ISHE in a stripe microstucture excited by a\nmicrowave coplanar waveguide (CPW) antenna. By using their different angular\ndependencies, we distinguish between spin rectification effects and the inverse\nspin Hall effect. The relatively large value of the spin Hall angle $(5.7 \\pm\n1.4)\\: \\% $ hints that interface engineering by epitaxially grown non-magnetic\nmaterials can increase the spin-to-charge current conversion efficiency.\n