Interfacial spin Hall effect and spin swapping in Fe-Au bilayers from first principles

Abstract

The interfaces in hybridized structures could give rise to rich phenomena, which open the way to novel devices with extraordinary performance. Here, we investigate the interface-related spin transport properties in Fe|Au bilayer based on first-principle calculation. We find that the spin Hall current in the Au side near the interface flows in the opposite direction to the bulk spin Hall current with the magnitude sensitive to the magnetization direction of Fe. This negative interfacial contribution is attributed to the spin dependent transmission within a few atomic layers, where a strong interfacial Rashba spin-orbit coupling exists. Surprisingly, the interfacial spin Hall currents are found to be not confined at the interface but extend tens of nanometers at low temperature, which is limited by momentum scattering and therefore much shorter than the spin diffusion length. In addition, the interfacial swapping spin currents, as a consequence of the spin precession under the interfacial Rashba field, are also obtained from our calculation and complete the full spin transport picture with all non-vanishing components. Our results suggest the importance of the interface engineering in spin-related transport in ferromagnetic|non-magnetic heterostructures and the possibility of manipulating the interfacial transport by the magnetization orientation of the magnetic layer.

Spin–orbit magnetic state readout in scaled ferromagnetic/heavy metal nanostructures

“…The deviation at lower temperatures could be caused by slight mismatches between the used parameters of the literature and the actual parameters. Alternatively, the presence of a strong interfacial spin-to-charge conversion at the FM/Pt interface 31 could be a relevant contribution in the thinnest Pt, an effect that might be more significant at low temperatures 32 . For a more accurate calculation, we use a 3D finite-element-method (FEM) to calculate the spin Hall signal, plotted as a green dashed line in Figs.…”

Large spin-charge interconversion induced by interfacial spin-orbit coupling in a highly conducting all-metallic system

“…( 1) and ( 2)] and, independently of the origin, quantify it by two phenomenological parameters: the interfacial spin-to-charge conductivity σ sc/cs and the interfacial spin-loss conductance G . A related effect is the interfacial SHE, which also originates from the interfacial SOC, as in the case of the Fe/Au interface [34]. However, the CS conversion studied in this work corresponds to a different experimental situation and therefore cannot be used to explain our observations.…”

“…This observation, together with its very high conductivity, makes Au a promising candidate to decrease current densities in CS conversion-based devices. Indeed, large spin-charge interconversion has been reported in very thin Au films [31][32][33] and first-principles calculations suggest it is related to an interfacial effect [34]. This interfacial contribution might be at the origin of the large dispersion of reported spin Hall angles in Au [10].…”

Calculating interface transport parameters at finite temperatures: Nonmagnetic interfaces

“…For electrons with an in-plane velocity component along −y (i.e. top panel), the spin-up electrons (red) find it easier to pass through the interface because the potential barrier they see at the interface is reduced by the Rashba field while that of the spin-down (blue) electrons is increased and they are reflected more [71]. For electrons with an in-plane velocity component along +y (i.e.…”