Nonlocal electrical detection of spin accumulation generated by Anomalous Hall effects in mesoscopic Ni_81Fe_19 films

TL;DR

This study demonstrates electrical detection of spin accumulation caused by anomalous Hall effects in mesoscopic Ni81Fe19 films, revealing key spin transport parameters and their temperature dependence.

Contribution

It provides a quantitative analysis of spin diffusion length and spin Hall angle in Ni81Fe19 films using a nonlocal measurement technique, with temperature-dependent results.

Findings

Spin diffusion length in Py is much shorter than film thickness.

The product of spin Hall angle and spin diffusion length is constant across thickness and resistivity.

Spin Hall angle values are comparable to those in mesoscopic Pt films.

Abstract

Spin accumulation generated by the anomalous Hall effects (AHE) in mesoscopic ferromagnetic Ni81Fe19 (permalloy or Py) films is detected electrically by a nonlocal method. The reciprocal phenomenon, inverse spin Hall effects (ISHE), can also be generated and detected all-electrically in the same structure. For accurate quantitative analysis, a series of nonlocal AHE/ISHE structures and supplementary structures are fabricated on each sample substrate to account for statistical variations and to accurately determine all essential physical parameters in-situ. By exploring Py thicknesses of 4 nm, 8 nm, and 12 nm, the Py spin diffusion length {\lambda}_Py is found to be much shorter than the film thicknesses. The product of {\lambda}_Py and the Py spin Hall angle {\alpha}_SH is determined to be independent of thickness and resistivity: {\alpha}_SH*{\lambda}_Py= (0.066 +/- 0.009) nm at 5 K and (0.041 +/- 0.010) nm at 295 K. These values are comparable to those obtained from mesoscopic Pt films.