The Rashba effect is an interaction between the spin and the momentum of electrons induced by the spin-orbit coupling (SOC) in surface or interface states. Its potential for conversion between charge and spin currents has been theoretically predicted but never clearly demonstrated for surfaces or interfaces of metals. Here we present experiments evidencing a large spin-charge conversion by the Bi/Ag Rashba interface. We use spin pumping to inject a spin current from a NiFe layer into a Bi/Ag bilayer and we detect the resulting charge current. As the charge signal is much smaller (negligible) with only Bi (only Ag), the spin-to-charge conversion can be unambiguously ascribed to the Rashba coupling at the Bi/Ag interface. This result demonstrates that the Rashba effect at interfaces can be used for efficient chargespin conversion in spintronics.

Through combined ferromagnetic resonance, spin pumping, and inverse spin Hall effect experiments in Co|Pt bilayers and Co|Cu|Pt trilayers, we demonstrate consistent values of ℓsfPt=3.4±0.4  nm and θSHEPt=0.056±0.010 for the respective spin diffusion length and spin Hall angle for Pt. Our data and model emphasize the partial depolarization of the spin current at each interface due to spin-memory loss. Our model reconciles the previously published spin Hall angle values and explains the different scaling lengths for the ferromagnetic damping and the spin Hall effect induced voltage.

The spin-orbit interaction couples the electrons' motion to their spin. Accordingly, passing a current in a material with strong spin-orbit coupling generates a transverse spin current (spin Hall effect, SHE) and vice-versa (inverse spin Hall effect, ISHE) 1-3 . The emergence of SHE and ISHE as charge-to-spin interconversion mechanisms offers a variety of novel spintronics functionalities 4,5 and devices, some of which do not require any ferromagnetic material 6 . However, the interconversion efficiency of SHE and ISHE (spin Hall angle) is a bulk property that rarely exceeds ten percent, and does not take advantage of interfacial and low-dimensional effects otherwise ubiquitous in spintronics hetero-and mesostructures. Here, we make use of an interface-driven spin-orbit coupling mechanism  the Rashba effect 7  in the oxide two-dimensional electron system (2DES) LaAlO3/SrTiO3 to achieve spin-to-charge conversion with unprecedented efficiency. Through spin-pumping, we inject a spin current from a NiFe film into the oxide 2DES and detect the resulting charge current, which can be strongly modulated by a gate voltage. We discuss the amplitude of the effect and its gate dependence on the basis of the electronic structure of the 2DES. Perovskite oxide materials possess a broad range of functionalities, some of which can be very appealing for spintronics. This includes half-metallicity in mixed-valence manganites  that can be used to produce giant tunnel magnetoresistance 8  or multiferroicity  through which magnetization direction can be electrically controlled at low power 9 . The recent years have seen the emergence of novel spintronics effects based on the generation and control of pure spin currents through spin-orbit effects in semiconducting and metallic systems 1-3 . However, despite a renewal of interest for 4d and 5d transition metal perovksites 10 , spin-orbit effects remained largely unexplored in oxide spintronics.An emerging direction in oxide research aims at discovering novel electronic phases at interfaces between two oxide materials 11 . A well-known example is the LaAlO3/SrTiO3 system: while both LaAlO3 (LAO) and SrTiO3 (STO) are wide bandgap semiconductors, a high-mobility two-dimensional electron system (2DES) forms at their interface 12 if the LAO thickness is at least 4 unit-cells (uc). Interestingly, LAO/STO possesses several remarkable extra functionalities including a gate-tuneable Rashba effect 13,14 , which makes it particularly appealing for spintronics.The Rashba effect is a manifestation of the spin-orbit interaction (SOI) in solids, where spin degeneracy associated with the spatial inversion symmetry is lifted due to a symmetry-breaking electric field normal to an heterointerface 15 . In a Rashba 2DES, the flow of a charge current results in the creation of a nonzero spin accumulation 16,17 coming from uncompensated spin-textured Fermi surfaces. Recently, the converse effect so-called inverse Edelstein effect (IEE)  that is a spin-to-charge conversion through SOI  was discovered a...

Direct observations of current-induced domain-wall propagation by spin-polarized scanning electron microscopy are reported. Current pulses move head-to-head as well as tail-to-tail walls in submicrometer Fe20Ni80 wires in the direction of the electron flow, and a decay of the wall velocity with the number of injected current pulses is observed. High-resolution images of the domain walls reveal that the wall spin structure is transformed from a vortex to a transverse configuration with subsequent pulse injections. The change in spin structure is directly correlated with the decay of the velocity.

1We present experimental results on the conversion of a spin current into a charge current by spin pumping into the Dirac cone with helical spin polarization of the elemental topological insulator (TI) α- The Inverse Edelstein Effect 5,6,17 (IEE) can be described as the inverse conversion of the one in EE. As depicted in Fig.1e-f, the injection of a vertical spin current into the 2DEG at a Rashba or TI surface/interface induces a charge current in the 2DEG. The IEE length 5  IEE is the ratio between the 2D conventional charge current density (in A/m) induced by IEE in the surface/interface 2DEG and the injected 3D spin current density, . We adopt the usual definition with the injected spin current density with equal to the difference between the injected charge current densities carried by electrons having their spin respectively oriented along the +i and -i directions along the x-or y-axis (the corresponding injected spin flow density is /(2e) where e= -|e|). For both Rashba and TI interfaces, and in the simple situation of circular spin contours,  IEE can be expressed as a function of the relaxation time τ of an out of equilibrium distribution in the topological states by the following, where α R is the Rashba coefficient, and, as derived infor TI, where v F is the Fermi velocity of the DC. To be more precise on the sign, our definition of the IEE length is exactlywhere the upper ( In the ARPES images of Fig. 2, a DC is clearly seen at the free surface (top) of our α-Sn (001) Supplementary Fig. 2). We can thus expect that only the α-Sn/Ag/Fe samples will show SCC by IEE. This is confirmed by the results displayed in Fig. 3b-c: i) A large enhancement of the damping coefficient revealing significant spin absorption is seen in Fig. 3b only for α-Sn/Ag/Fe and not for α-Sn/Fe. ii) In Fig. 3c, a dc charge current I C peak at the resonance is only seen for α- An important parameter in equation (1) ARPES measurements. The ARPES measurements were performed at room temperature with incident photon energy of 19 eV and resolving angle between 15° which correspond to wave number k between 5 nm -1 at the Fermi level. In Fig. 2, only the area of interest is shown.Ferromagnetic resonance (FMR) and spin pumping. The samples have the stacking order shown in Fig. 3.The broadband frequency dependence was performed in a coplanar wave guide system, applying the external magnetic film at different in-plane crystalline directions of the substrate. The samples were then cut in slab of 2.4x0.4 mm to carry out the simultaneously FMR and transversal dc voltage measurement (Fig. 3a,c). The slab is placed on the axis of a cylindrical X-band cavity (frequency ≈ 9.6 GHz). The charge current I C is derived from the voltage V needed to cancel it, I c = V/R where R is the resistance of the sample measured between the voltage probes.5

We have studied the evolution of the Spin Hall Effect in the regime where the material size responsible for the spin accumulation is either smaller or larger than the spin diffusion length. Lateral spin valve structures with Pt insertions were successfully used to measure the spin absorption efficiency as well as the spin accumulation in Pt induced through the spin Hall effect. Under a constant applied current the results show a decrease of the spin accumulation signal is more pronounced as the Pt thickness exceeds the spin diffusion length. This implies that the spin accumulation originates from bulk scattering inside the Pt wire and the spin diffusion length limits the SHE. We have also analyzed the temperature variation of the spin hall conductivity to identify the dominant scattering mechanism.PACS numbers: 72.25. Ba, 72.25.Mk, 75.70.Cn, 75.75.+a Recently a long-standing prediction of Spin Hall Effect (SHE) [1,2,17] has been verified by means of both optical [3,4,5,12] and magneto-transport [6,7,8] measurements. The SHE originates from the spin-orbit coupling, which relates the spin of an electron to its momentum, producing a spin current in the direction transverse to the flow of electrons and a spin accumulation at lateral sample boundaries. This is the direct SHE (DSHE) where unpolarized charge currents are converted into pure spin currents with zero net charge flow. There is also the inverse effect called inverse SHE (ISHE) where a pure spin currents can be converted into charge currents by the spin-orbit interaction. The SHE is therefore regarded as a new tool for generating and detecting spin currents, crucial issues for future spintronics, that in principle does not require ferromagnetic elements and/or external magnetic field.The SHE induced spin accumulation in Semiconductors (SCs) have drawn much attention because of its compatibility with conventional CMOS technology. However, up to now SCs have exhibited very small SHE and no electrical detection has been reported yet. On the contrary Pt metal has been successfully used to detect the SHE even at room temperature, exhibiting the largest spin Hall conductivity reported so far [7]. The possible origins of the SHE can be classified in two categories, intrinsic and extrinsic, depending on the dominant influence of either band structure or impurities [9]. The SHE is also expected to be strongly geometry dependent. In metals like Pt, the SHE may be mainly attributable to extrinsic mechanisms such as the side jump and the skew scattering, which are responsible for the anomalous Hall effect in ferromagnets. The different sign of the side jump or the skew scattering angle for the two spin channels results in the transverse spin current and spin accumulation at lateral boundaries. One should also remark here that recent theoretical analysis based on the first principle band calculation strongly suggests that the origin of the large SHE in Pt is of intrinsic nature [10]. Thus it is important to perform systematically experiments in order to better underst...

Torques appear between charge carrier spins and local moments in regions of ferromagnetic media where spatial magnetization gradients occur, such as a domain wall, owing to an exchange interaction. This phenomenon has been predicted by different theories 1-7 and confirmed in a number of experiments on metallic and semiconductor ferromagnets 8-19. Understanding the magnitude and orientation of such spin-torques is an important problem for spin-dependent transport and currentdriven magnetization dynamics, as domain-wall motion underlies a number of emerging spintronic technologies 20,21. One outstanding issue concerns the non-adiabatic spin-torque component β, which has an important role in wall dynamics, but no clear consensus has yet emerged over its origin or magnitude. Here, we report an experimental measurement of β in perpendicularly magnetized films with narrow domain walls (1-10 nm). By studying thermally activated wall depinning, we deduce β from the variation of the Arrhenius transition rate with applied currents. Surprisingly, we find β to be small and relatively insensitive to the wall width, which stands in contrast to predictions from transport theories 2,5-7. In addition, we find β to be close to the Gilbert damping constant α, which, in light of similar results on planar anisotropy systems 15 , suggests a universal origin for the non-adiabatic torque. The adiabatic torque, which accounts for transport processes in which the conduction spin follows the local spatial magnetization variation by remaining in either the majority or minority state, is well understood and has been reproduced by a number of different transport theories. In contrast, the non-adiabatic contribution, characterized by a dimensionless parameter β (ref. 22), remains the subject of much debate. Various mechanisms have been put forward to explain its origin, such as momentum transfer 2,7 , spinmistracking 4,6 or spin-flip scattering 3. It is predicted that large nonadiabatic effects should appear in narrow domain walls because of large magnetization gradients 2,5,6 , whereby the wall width becomes comparable to important transport scales such as the spin-diffusion length 2 or the Larmor precession length 6 , which are of the order of a few nanometres in ferromagnetic transition metals. The presence of a non-adiabatic term is of fundamental importance, because its existence implies that current-driven wall motion is possible for any finite current in a perfect system, even in the absence of an applied magnetic field. Difficulty in characterizing β experimentally therefore stems in part from being able to distinguish between extrinsic sources of wall pinning, due to structural defects, for example, from the intrinsic finite threshold current predicted 2 for β = 0. We have studied current-driven domain wall dynamics in two different pseudo spin-valve systems based either on CoNi

The capacity to propagate magnetic domain walls with spin-polarized currents underpins several schemes for information storage and processing using spintronic devices. A key question involves the internal structure of the domain walls, which governs their response to certain current-driven torques such as the spin Hall effect. Here we show that magnetic microscopy based on a single nitrogen-vacancy defect in diamond can provide a direct determination of the internal wall structure in ultrathin ferromagnetic films under ambient conditions. We find pure Bloch walls in Ta/CoFeB(1 nm)/MgO, while left-handed Néel walls are observed in Pt/Co(0.6 nm)/AlO x . The latter indicates the presence of a sizable interfacial Dzyaloshinskii-Moriya interaction, which has strong bearing on the feasibility of exploiting novel chiral states such as skyrmions for information technologies.