Spin current generation from an epitaxial tungsten dioxide WO$_{2}$

Kohei Ueda; Hayato Fujii; Takanori Kida; Masayuki Hagiwara; Jobu Matsuno

doi:10.1063/5.0153533

paper

Spin current generation from an epitaxial tungsten dioxide WO $_{2}$

arXiv:2305.17887 · doi:10.1063/5.0153533

Abstract

We report on efficient spin current generation at room temperature in rutile type WO $_{2}$ grown on Al $_{2}$ O $_{3}$ (0001) substrate. The optimal WO $_{2}$ film has (010)-oriented monoclinically distorted rutile structure with metallic conductivity due to 5 $d$ $^{2}$ electrons, as characterized by x-ray diffraction, electronic transport, and x-ray photoelectron spectroscopy. By conducting harmonic Hall measurement in Ni $_{81}$ Fe $_{19}$ /WO $_{2}$ bilayer, we estimate two symmetries of the spin-orbit torque (SOT), i.e., dampinglike (DL) and fieldlike ones to find that the former is larger than the latter. By comparison with the Ni $_{81}$ Fe $_{19}$ /W control sample, the observed DL SOT efficiency $ξ$ $_{D L}$ of WO $_{2}$ (+0.174) is about two thirds of that of W (-0.281) in magnitude, with a striking difference in their signs. The magnitude of the $ξ$ $_{D L}$ of WO $_{2}$ exhibits comparable value to those of widely reported Pt and Ta, and Ir oxide IrO $_{2}$ . The positive sign of the $ξ$ $_{D L}$ of WO $_{2}$ can be explained by the preceding theoretical study based on the 4 $d$ oxides. These results highlight that the epitaxial WO $_{2}$ offers a great opportunity of rutile oxides with spintronic functionalities, leading to future spin-orbit torque-controlled devices.

arXiv comment14 pages, 4 figures

Spin current generation from an epitaxial tungsten dioxide WO $_{2}$

Abstract

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Spin current generation from an epitaxial tungsten dioxide WO2​

Abstract

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Spin current generation from an epitaxial tungsten dioxide WO $_{2}$