Control of the spin to charge conversion using the inverse Rashba-Edelstein effect

Abstract

We show here that using spin orbit coupling interactions at a metallic interface it is possible to control the sign of the spin to charge conversion in a spin pumping experiment. Using the intrinsic symmetry of the "Inverse Rashba Edelstein Effect" (IREE) in a Bi/Ag interface, the charge current changes sign when reversing the order of the Ag and Bi stacking. This confirms the IREE nature of the conversion of spin into charge in these interfaces and opens the way to tailoring the spin sensing voltage by an appropriate trilayer sequence. V C 2015 AIP Publishing LLC.[http://dx.doi.org/10.1063/1.4919129] Classical spintronics relies on the generation and manipulation of spin polarized electrical currents in magnetic conductors. It has been recently understood that spin currents can also be generated in non-magnetic materials using the spin-orbit coupling (SOC) interaction opening a new field called spin-orbitronics. The best known of these is the Spin Hall Effect (SHE) first introduced in the seventies.1,2 It relies on a preferential directional scattering of electrons of different spins by SOC on crystalline imperfections. It thus results in the generation of a transverse spin current when a charge current flows in a large SOC material like, for instance, Pt. The inverse SHE (ISHE) has been widely used lately to sense a spin current as the SOC interaction converts it into a (transverse) charge current. Very recently, another SOC effect based on the Rashba interaction has been evidenced. It stems from the joint action of the SOC and built-in electric potentials in two-dimensional electron gases (2DEGs) existing at surfaces, interfaces, or semiconductor quantum wells. In these systems, a charge current generates a non-zero spin density and transverse spin accumulation 3,4 in virtue of the Rashba Hamiltonianwhere s is the spin vector, k is the momentum of charge carriers, z is the coordinate normal to the interface, and a R is the Rashba coefficient, proportional to the induced internal electric field. When in contact with a magnetic material, this spin density can apply a torque on the magnetization, a mechanism put forward to explain experimental results on current induced domain wall motion and magnetization switching. 5,6Recently, a related effect, the Inverse Rashba Edelstein Effect (IREE) has been demonstrated 7 where a spin current generated by ferromagnetic resonance (FMR) 8 in a magnetic layer, is converted into a charge current when flowing through an adjacent Ag/Bi interface. Bi (111) is indeed known to produce interface states with many materials where strong Rashba coupling takes place 9,10 and the Bi/Ag interface is known to be a particularly good one.7 Interestingly, because the asymmetrical potential at the interface is responsible for generating the transverse spin/charge density, one can envision to tailor the spin to charge conversion by shaping the asymmetric well. In particular, and quite straightforwardly, the charge current direction should be reversed when Ag/Bi is replaced by Bi/Ag, i.e., t...

Spin Hall Magnetoresistance as a Probe for Surface Magnetization inPt/CoFe2O4Bilayers

“…Many different phenomena arising from spin-orbit coupling, such as magnetic skyrmions [2][3][4], the Rashba and Dresselhaus effects [5][6][7], the spin Hall effect (SHE) [8,9] or the spin-orbit torques for magnetic switching of ferromagnetic elements [10,11] are intensively being explored. Of particular interest is the SHE, a phenomenon in which an unpolarized charge current flowing through a NM metal with strong SOC is converted into a transverse spin current due to the opposite scattering of spin-up and spin-down electrons [8,9].…”

Quantitative investigation of the inverse Rashba-Edelstein effect in Bi/Ag and Ag/Bi on YIG

“…However, simultaneously, it is noted that NiFe or Fe was used as a spin source of spin pumping in ref. [11,15,23]. We note that IREE length can depend on the interface quality, and, thus, vary between different studies.…”

“…Polarity of the electric current in the Ag/Bi/YIG was not reversed, although the direction of the Rashba field is opposite for the two types of samples. To interpret the experimental data, we constructed a model that includes generation of the spin-charge conversion current by both the IREE and the ISHE, which was partly considered in the study [15], and also considers spin transparency, κ, of the Ag/Bi interface. The IREE lengths calculated for the κ = 0 and κ = 1 are the upper and the lower limits, respectively.…”

Efficient charge-spin conversion and magnetization switching through the Rashba effect at topological-insulator/Ag interfaces

“…However, due to the bulk nature of SHE, a certain thickness of heavy metals is required to achieve a sufficient spin current density. Recently, Rashba induced charge-spin interconversions, with a higher efficiency than that from SHE, have been detected in Bi/Ag, α-Sn/Ag [7][8][9][10], LaAlO3/SrTiO3 [11]. On the other hand, the topological surface states (TSS) of topological insulators (TIs) are another interfacial mechanism for achieving efficient charge-to-spin conversion due to the strong spin orbit coupling (SOC) and inherent spinmomentum locking, despite of the inevitable bulk transport [3,4,[12][13][14][15][16][17].…”