Electronic spin transport in graphene field-effect transistors

Popinciuc, M.; Józsa, C.; Zomer, P. J.; Tombros, N.; Veligura, A.; Jonkman, Harry T.; Wees, van Bart

doi:10.1103/physrevb.80.214427

Cited by 192 publications

(294 citation statements)

References 45 publications

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“…(1) in the z direction and use the BrataasNazarov-Bauer boundary condition at the NM/FMI interface [5]. From the solution one can obtain an expression for the nonlocal resistance at the FM detector that reads [37,42,43]…”

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Modulation of pure spin currents with a ferromagnetic insulator

et al. 2015

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We propose and demonstrate spin manipulation by magnetically controlled modulation of pure spin currents in cobalt/copper lateral spin valves, fabricated on top of the magnetic insulator Y 3 Fe 5 O 12 (YIG). The direction of the YIG magnetization can be controlled by a small magnetic field. We observe a clear modulation of the nonlocal resistance as a function of the orientation of the YIG magnetization with respect to the polarization of the spin current. Such a modulation can only be explained by assuming a finite spin-mixing conductance at the Cu/YIG interface, as it follows from the solution of the spin-diffusion equation Spintronics is a rapidly growing field that aims at using and manipulating not only the charge, but also the spin of the electron, which could lead to faster data processing, nonvolatility, and lower electrical power consumption as compared to conventional electronics [1]. Sophisticated applications such as hard-disk read heads and magnetic random access memory (MRAM) have been introduced in the last two decades.Further progress could be achieved with pure spin currents, which are an essential ingredient in an envisioned spin-only circuit that would integrate logics and memory [2]. The most basic unit in such a concept is the spin analog to the transistor, in which the manipulation of pure spin currents is crucial. The original proposal by Datta and Das [3], which is also applicable to pure spin currents [4], suggested a spin manipulation that would arise from the spin precession due to the spin-orbit interaction modulated by an electric field (Rashba coupling). However, a fundamental limitation appears here, because the best materials for spin transport are those showing the lowest spin-orbit interaction and, therefore, there has been no success in electrically manipulating the spins and propagating them at the same environment, with few exceptions [4].Alternative ways to control pure spin currents are thus desirable. One could take advantage of the spin-mixing conductance concept [5,6] at nonmagnetic metal (NM)/ferromagnetic insulator (FMI) interfaces, which governs the interaction between the spin currents present at the NM and the magnetization of the FMI. This concept is the basis of new spindependent phenomena, including spin pumping [6][7][8][9][10][11][12], spin Seebeck effect [6,13], and spin Hall magnetoresistance (SMR) [6,[14][15][16][17][18]. In these cases, a NM with large spin-orbit coupling is required to convert the involved spin currents into charge currents via the inverse spin Hall effect [19].In this Rapid Communication, we demonstrate an alternative way of modulating pure spin currents based on a magnetic, instead of electric, gating. To that end, we use lateral spin valves (LSVs). These devices allow an electrical injection and detection of pure spin currents in a NM channel by using * f.casanova@nanogune.eu ferromagnetic (FM) electrodes in a nonlocal configuration [20][21][22][23][24][25][26][27][28][29]. The LSVs have been fabricated on top of a FMI, in order to enab...

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Modulation of pure spin currents with a ferromagnetic insulator

et al. 2015

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“…This makes graphene an indispensable material for the further development of nanoelectronics. Moreover, owing to the large spin-relaxation length, it can be effectively used in spintronics as a material for graphene spin filters and for graphene field-effect transistors [5][6][7][8][9]. However, up to now graphene is used in spintronics only as a passive element due to the low magnitude of the spin-orbit splitting of graphene π states.…”

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Nontrivial spin structure of graphene on Pt(111) at the Fermi level due to spin-dependent hybridization

et al. 2014

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The electronic and spin structure of a graphene monolayer synthesized on Pt(111) has been investigated experimentally by angle-and spin-resolved photoemission with different polarizations of incident synchrotron radiation and using density functional theory calculations. It is shown that despite the observed total quasifreestanding character of the dispersion of the graphene π state remarkable local distortions and breaks in the dispersions take place due to hybridization between the graphene π and Pt d states. Corresponding spin-dependent avoided-crossing effects lead to significant modification of the spin structure and cause an enhanced induced spin-orbit splitting of the graphene π states near the Fermi level in the region of theK point of the graphene Brillouin zone (BZ) with a magnitude of 80-200 meV depending on the direction in the BZ. Using p, s, and elliptical polarizations of the synchrotron radiation, the contributions of the graphene π and Pt d states were separated and their intersection at the Fermi level, which is important for effective spin injection between these states, was shown. Moreover, analysis of the data allows us to conclude that in the region of the Dirac point the spin structure of the system cannot be described by a Rashba splitting, and even a spin-orbit gap between lower and upper Dirac cones is observed.

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“…Complicating the situation are the many possible sources of spin relaxation in experiments on SiO 2 substrate including charged impurity (CI) scatterers, 16,17 Rashba SO coupling due toadatoms, 18,19,25 ripples, 20,21 and edge effects. 17,23 Early experiments on spin transport in exfoliated graphene were able to take advantage of the tunable carrier concentration (n) and observe a linear relationship between τ s and τ p , thus suggesting EY. 15,22 However, recent theoretical studies have shown that DP is expected to dominate over EY 21,24 and that Elliot's approach applied to graphene 17 predicts τ s = ( F ) 2 τ p /(∆ SO ) 2 , for which both Fermi energy F and τ p depend on carrier concentration, thus highlighting the need for experiments that can tune τ p at fixed n. * roland.kawakami@ucr.edu…”

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“…In graphene, two possible spin relaxation mechanisms are discussed in the literature: [14][15][16][17][18][19][20][21][22][23][24] the Elliot-Yafet (EY) mechanism, for which the spin relaxation time (τ s ) is proportional to the momentum scattering time (τ p ), and the D'yakonov-Perel (DP) mechanism, for which τ s ∝ 1/τ p . Complicating the situation are the many possible sources of spin relaxation in experiments on SiO 2 substrate including charged impurity (CI) scatterers, 16,17 Rashba SO coupling due toadatoms, 18,19,25 ripples, 20,21 and edge effects.…”

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Effect ofin situdeposition of Mg adatoms on spin relaxation in graphene

et al. 2013

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We have systematically introduced charged impurity scatterers in the form of Mg adsorbates to exfoliated single layer graphene and observe little variation of the spin relaxation times despite pronounced changes in the charge transport behavior. All measurements are performed on non-local graphene tunneling spin valves exposed in-situ to Mg adatoms, thus systematically introducing atomic-scale charged impurity scattering. While charge transport properties exhibit decreased mobility and decreased momentum scattering times, the observed spin lifetimes are not significantly affected indicating that charged impurity scattering is inconsequential in the present regime of spin relaxation times (∼1 ns).

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Electronic spin transport in graphene field-effect transistors

Cited by 192 publications

References 45 publications

Modulation of pure spin currents with a ferromagnetic insulator

Modulation of pure spin currents with a ferromagnetic insulator

Nontrivial spin structure of graphene on Pt(111) at the Fermi level due to spin-dependent hybridization

Effect ofin situdeposition of Mg adatoms on spin relaxation in graphene

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