Current-induced spin–orbit torques

Gambardella, Pietro; Miron, Ioan Mihai

doi:10.1098/rsta.2010.0336

Cited by 344 publications

(329 citation statements)

References 99 publications

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“…Equation 1) in a simple model based on the standard picture of the REEs. For the two Fermi contours of Rashba 2D electrons, the relation between the 2D spin densities ds ± along the x axis and the 2D charge current densities along y can be written as 22 :…”

Section: Methodsmentioning

confidence: 99%

“…The frequency dependence of the linewidth has been used in order to discriminate the contribution from spin pumping and frequency independent contribution due to inhomogeneities. The difference between the damping in the studied sample, a eff , and the damping in a single NiFe(15) reference layer,a 0 , gives the effective spin mixing conductivity 22 :…”

Section: Methodsmentioning

confidence: 99%

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Spin-to-charge conversion using Rashba coupling at the interface between non-magnetic materials

et al. 2013

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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.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Spin-to-charge conversion using Rashba coupling at the interface between non-magnetic materials

et al. 2013

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“…1,16,18,23,24 The SOCs in the bulk or on the surface of ferromagnetic materials play crucial role in other phenomena, such as the anomalous Hall effect 25 or the tunneling anisotropic magnetoresistance [26][27][28][29][30][31] (TAMR). Moreover, the study of the interplay between SOC and STT has been recently initiated 9,32-34 through theoretical proposals 35 and experimental realizations 22,36 that exploit SOCs for STT-driven magnetization reversal of a single F layer with greatly reduced critical current required when compared to traditional spin valves or MTJs with two non-collinear magnetizations. 10 In the "standard model" 1,7 of spin pumping in magnetic multilayers containing many 7 F and N layers, the magnitude of pumped spin current by F|N interfaces is computed quantum-mechanically via the Brouwer scattering formula 37 which then serves as the boundary condition for the spin-diffusion equation 7 or enters into the so-called circuit theory 21 where device is split into nodes of characteristic size smaller than the spin-diffusion length.…”

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confidence: 99%

Charge pumping by magnetization dynamics in magnetic and semimagnetic tunnel junctions with interfacial Rashba or bulk extrinsic spin-orbit coupling

et al. 2012

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We develop a time-dependent nonequilibrium Green function (NEGF) approach to the problem of spin pumping by precessing magnetization in one of the ferromagnetic layers within F|I|F magnetic tunnel junctions (MTJs) or F|I|N semi-MTJs in the presence of intrinsic Rashba spin-orbit coupling (SOC) at the F|I interface or the extrinsic SOC in the bulk of F layers of finite thickness (F-ferromagnet; N-normal metal; I-insulating barrier). To express the time-averaged pumped charge current, or the corresponding dc voltage signal in an open circuit, we construct a novel solution to double-time-Fourier-transformed NEGF equations. The two energy arguments of NEGFs in this representation are connected by the Floquet theorem describing multiphoton emission and absorption processes. Within this fully quantum-mechanical treatment of the conduction electrons, we find that: (i) only in the presence of the interfacial Rashba SOC, the non-zero dc pumping voltage Vpump in F|I|N junctions can emerge at the adiabatic level (i.e., proportional to the microwave frequency), which could explain recent experiments on microwave-driven semi-MTJs [T. Moriyama et al., Phys. Rev. Lett. 100, 067602 (2008)]; (ii) a unique signature of this charge pumping phenomenon, where the Rashba SOC within the precessing F layer participates in the pumping process, is Vpump that changes sign as the function of the precession cone angle; (iii) unlike conventional spin pumping in MTJs in the absence of SOCs, where one emitted or absorbed microwave photon is sufficient to match the exact solution in the frame rotating with the magnetization, the presence of the Rashba SOC requires to take into account up to ten photons in order to reach the asymptotic value of pumped charge current; (iv) the disorder within F|I|F MTJs can enhance Vpump in the quasiballistic transport regime; (v) the extrinsic SOC in F|I|F MTJs causes spin relaxation and eventually the decay of Vpump which becomes negligible when the ratio of F layer thickness to the spin-diffusion length is around five. Our formalism can also be applied to electron and spin propagation in any noninteracting quantum system which is brought out of equilibrium by external fields of arbitrary strength or frequency.

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“…Of such devices, the most common is nanostructured ferromagnetic thin films with perpendicular magnetic anisotropy (PMA) [2]. The effective field induced by the PMA − namely, the magnetic anisotropy field − has been found to play an important role in magnetization dynamics driven by the spin-orbit torque (SOT) [3][4][5][6]. Therefore, precise measurement of the magnetic anisotropy field is becoming crucial nowadays to understand the SOT-induced magnetization dynamics as well as to quantify the magnitude of the SOT.…”

Section: Introductionmentioning

confidence: 99%

Optical Measurement of Magnetic Anisotropy Field in Nanostructured ferromagnetic Thin Films

Whang¹,

Yun²,

Moon³

et al. 2015

Journal of Magnetics

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The magnetic anisotropy field plays an important role in spin-orbit-torque-induced magnetization dynamics with electric current injection. Here, we propose a magnetometric technique to measure the magnetic anisotropy field in nanostructured ferromagnetic thin films. This technique utilizes a magneto-optical Kerr effect microscope equipped with two-axis electromagnets. By measuring the out-of-plane hysteresis loops and then analyzing their saturated magnetization with respect to the in-plane magnetic field, the magnetic anisotropy field is uniquely quantified within the context of the Stoner-Wohlfarth theory. The present technique can be applied to small nanostructures, enabling in-situ determination of the magnetic anisotropy field of nanodevices.

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Current-induced spin–orbit torques

Cited by 344 publications

References 99 publications

Spin-to-charge conversion using Rashba coupling at the interface between non-magnetic materials

Spin-to-charge conversion using Rashba coupling at the interface between non-magnetic materials

Charge pumping by magnetization dynamics in magnetic and semimagnetic tunnel junctions with interfacial Rashba or bulk extrinsic spin-orbit coupling

Optical Measurement of Magnetic Anisotropy Field in Nanostructured ferromagnetic Thin Films

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