Spin-Orbit Interaction Induced Spin-Separation In Platinum Nanostructures

Abstract

We have demonstrated electrical generation and detection of spin polarization by the spin Hall effect in platinum. The spin Hall effect refers to the generation of a transverse spin current, and the subsequent non-equilibrium spin accumulation near sample boundaries. This occurs when a longitudinal electrical current is applied to materials with spin-orbit interaction. Spin polarization in metals is usually small and requires ferromagnetic metals to create and detect spin polarization. This ferromagnetic-based approach is suitable to be used as a laboratory investigation of spin transport phenomenon, but it limits the performance and scalability of the spintronics devices. Therefore, we designed and experimentally demonstrated using a non-local lateral geometry structure to investigate the generation and detection of spin polarization based on the spin Hall effect, without the need for magnetic materials, external magnetic field, or bulky optical systems.

The geometry made use of the spin Hall effect effect to generate spin polarization and its reciprocal effect, the inverse spin Hall effect, to detect spin polarization. A large spin Hall effect signal was observed from 10 K up to room temperature, which was the largest value reported so far in the literature. The measurements were also done using gold and aluminum samples. Aluminum failed to demonstrate any signal while gold showed weak signals compared to platinum in spite of similar atomic number. This suggested that the spin Hall effect in platinum was unusual. The drift-diffusion model was found to be adequate to model the spin transport in platinum. Based on the experimental results, the spin Hall effect in platinum was expected to be extrinsic. However, the extrinsic contribution to the observed effect was not fully understood and further investigation is needed.