Abstract
The spin Hall effect and the inverse spin Hall effect are important spin-charge conversion mechanisms. The direct spin Hall effect induces a surface spin accumulation from a transverse charge current due to spin-orbit coupling even in nonmagnetic conductors. However, most detection schemes involve additional interfaces, leading to large scattering in reported data. Here we perform interface-free x-ray spectroscopy measurements at the Cu absorption edges of highly Bi-doped Cu (). The detected x-ray magnetic circular dichroism signal corresponds to an induced magnetic moment of per Cu atom averaged over the probing depth, which is of the same order of magnitude as found for Pt measured by magneto-optics. The results highlight the importance of interface-free measurements to assess material parameters and the potential of CuBi for spin-charge conversion applications.
5 More- Received 5 July 2021
- Revised 11 February 2022
- Accepted 12 July 2022
DOI:https://doi.org/10.1103/PhysRevX.12.031032
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
Electrons carry small magnetic moments called spins, which are usually balanced in the absence of magnetism. But when an electrical current flows through a material, a spin imbalance can be produced as a result of spin-orbit coupling. This “spin Hall effect” is a promising method for the manipulation of magnetic textures such as domain walls in multilayer materials, which can be key for future energy-efficient memory and computing devices. However, most measurement methods probe the combined properties of those multilayers, mixing material and interface properties. In this work, we present a direct probe of the spin imbalance due to the spin Hall effect in a single layer of a copper bismuth alloy.
We use a dedicated electron microscope to detect electrons emitted from the upper surface of the electrode structure when the sample is illuminated by synchrotron light (x rays). The absorption of the circularly polarized x rays is sensitive to electron spins inside the sample at particular photon energies. This effect is the most direct and element-sensitive probe of the spin imbalance and can be linked to the induced magnetic moment. The microscope allows us to focus on very small electrodes and compare neighboring areas with opposite current direction, boosting the experimental sensitivity. Moreover, the probing depth of about 5 nm allows us to probe only the upper surface of the sample, which is key, as otherwise, the signals from the upper and lower surface would cancel out.
This novel approach can be extended to other materials and constitutes the first element-specific detection method of the spin Hall effect.