Lei Wang, R.J.H. Wesselink, Yi Liu, Zhe Yuan, Ke Xia, and Paul J. Kelly Phys. Rev. Lett. 116, 196602 (2016).
The spin Hall angle (SHA) is a measure of the efficiency with which a transverse spin current is generated from a charge current by the spin-orbit coupling and disorder in the spin Hall effect (SHE). In a study of the SHE for a Pt|Py (Py=Ni80Fe20) bilayer using a first-principles scattering approach, we find a SHA that increases monotonically with temperature and is proportional to the resistivity for bulk Pt. By decomposing the room temperature SHE and inverse SHE currents into bulk and interface terms, we discover a giant interface SHA that dominates the total inverse SHE current with potentially major consequences for applications.
Figure 1 (a) Schematic illustration of the scattering geometry. Electrons flow (jzc) from the perfectly crystalline left lead to the right one through a disordered region of pure bulk Pt where atoms are displaced from their equilibrium positions by populating phonons. Transverse spin currents arising from the SHE flowing along the x and −y directions are polarized in the y (jxsy) and x (jysx) directions, respectively. (b) Calculated transverse spin current densities in Pt normalized by jzc at room temperature. The error bars are a measure of the spread of ten random configurations. The dashed black line shows the extracted SHA. Inset: Integrated spin current density in a length LPt of disordered Pt. The dashed black line illustrates a linear least squares fit from which a SHA for pure bulk Pt of ΘsH = 0.0330.001 is extracted.