Observation of the nonlocal spin-orbital effective field

Abstract

The spin-orbital interaction in heavy nonmagnetic metal/ferromagnetic metal bilayer systems has attracted great attention and exhibited promising potentials in magnetic logic devices, where the magnetization direction is controlled by passing an electric current. It is found that the spin-orbital interaction induces both an effective field and torque on the magnetization, which have been attributed to two different origins: the Rashba effect and the spin Hall effect. It requires quantitative analysis to distinguish the two mechanisms. Here we show sensitive spin-orbital effective field measurements up to 10 nm thick ferromagnetic layer and find the effective field rapidly diminishes with the increase of the ferromagnetic layer thickness. We further show that this effective field persists even with the insertion of a copper spacer. The nonlocal measurement suggests that the spin-orbital effective field does not rely on the heavy normal metal/ferromagnetic metal interface.

Quantifying interface and bulk contributions to spin–orbit torque in magnetic bilayers

“…MOKE can also detect the in-plane magnetization with oblique angle incidence and therefore determine the SOF as described in the Methods section. However, in this manuscript, we choose to use the second-order PHE method to measure the SOF because of its better sensitivity 17 . As shown in Fig.…”

“…Combined with more sensitive SOF detection via the planar Hall effect (PHE) 17 , we obtain the thickness dependence of SOT and SOF over a wide range of FM thicknesses. On the basis of this technique, we are also able to quantitatively determine the bulk and interface contributions to the overall SOI effect.…”

Spin Torque Study of the Spin Hall Conductivity and Spin Diffusion Length in Platinum Thin Films with Varying Resistivity

“…Values of DL j ξ for Pt have been reported spanning the range 0.06 -0.12 [19,[27][28][29], depending on the FM/Pt interface [31], and are usually accompanied by a relatively small field-like (FL) torque efficiency whose magnitude and sign vary with the interface, FM magnetic anisotropy and temperature [29,[32][33][34][35][36]. From an analysis of SBF based on a spin diffusion model [24,25] is a well-known phenomenon due to strong diffusive scattering at a Pt surface [48,[53][54][55][56][57].…”

Anomalous temperature dependence of current-induced torques inCoFeB/MgOheterostructures with Ta-based underlayers

“…In many systems, however, the field-like torque is much larger than the damping-like torque 11,14 , and its direction is pointing opposite to the incoming spin direction of the electrons (assuming the spin source is the spin Hall effect) 11,14, 21 . Moreover, the size and direction of both components of the torque vary depending on the materials and the film structures [11][12][13][14] . Up to date, many of these results cannot be accounted for with existing theories that consider spin transfer and/or exchange torques 22, 23 .…”