Giant enhancement of spin accumulation and long-distance spin precession in metallic lateral spin valves

Fukuma, Yasuhiro; Wang, L.; Idzuchi, Hiroshi; Takahashi, Saburo; Maekawa, Sadamichi; Otani, Y.

doi:10.1038/nmat3046

Cited by 180 publications

(183 citation statements)

References 40 publications

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“…Here, a spin polarized charge current is applied between electrodes 1&2 and a non-local voltage is measured between electrodes 3&4 (Fig. 1a) 10 , all metallic spin valves (~ 20 mΩ) 32 and especially with bulk semiconductors (~ 20 mΩ) 33 .…”

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confidence: 99%

Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes

et al. 2017

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Two-dimensional materials offer new opportunities for both fundamental science and technological applications, by exploiting the electron's spin 1 . While graphene is very promising for spin communication due to its extraordinary electron mobility, the lack of a band gap restricts its prospects for semiconducting spin devices such as spin diodes and bipolar spin transistors 2 . The recent emergence of 2D semiconductors could help overcome this basic challenge. In this letter we report the first important step towards making 2D semiconductor spin devices. We have fabricated a spin valve based on ultra-thin (~ 5 nm) semiconducting black phosphorus (bP), and established fundamental spin properties of this spin channel material which supports all electrical spin injection, transport, precession and detection up to room temperature (RT). Inserting a few layers of boron nitride between the ferromagnetic electrodes and bP alleviates the notorious conductivity mismatch problem and allows efficient electrical spin injection into an n-type bP. In the non-local spin valve geometry we measure Hanle spin precession and observe spin relaxation times as high as 4 ns, with spin relaxation lengths exceeding 6 µm. Our experimental results are in a very good agreement with first-principles calculations and demonstrate that Elliott-Yafet spin relaxation mechanism is dominant. We also demonstrate that spin transport in ultra-thin bP depends strongly on the charge carrier concentration, and can be manipulated by the electric field effect. 2 Electron spin is an important degree of freedom which can complement or even replace charge in information storage and logic devices 3 . For spin-based electronics, it is essential to have materials with long spin relaxation times at RT 1 . With respect to the material selection, semiconductors in particular offer new opportunities that are unfeasible in metal-based spintronics devices. These include doping by the electric field effect and gate controlled amplification/switching actions 4 . The boom of semiconductor spintronics started with the demonstration of the electrical spin injection into GaAs by R. Fiederling et al., also later by H.Ohno et al. 5,6 . I. Appelbaum and his colleagues further fostered this by adding silicon into the spintronics materials family 7 . More recently 2D materials such as graphene have captured the interest of engineers and scientists on the grounds of their high electronic mobility and the simultaneous ability to tune their charge carrier concentrations by the electric field effect 8 .Graphene has already been investigated very extensively in the spintronics community since the first unequivocal demonstration of RT spin injection by N. Tombros et al., 1,9 . While the first devices showed spin lifetimes of only 0.1 ns 9 , the new generation of graphene devices that have surfaces within the last year show remarkable spin lifetimes of ~ 10 ns, making graphene suitable for spin communication channels 10 .Conversely, the zero-band gap nature of graphene does not al...

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confidence: 99%

Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes

et al. 2017

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“…λ is the spin-diffusion describes the well-known spin precession due to the applied field [40,41]. B is proportional to H and, for Cu, we can approximate B ∼ μ 0 H .…”

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confidence: 99%

“…Equation (3) shows that two quantities renormalize the spin-diffusion length: the spinmixing conductance by means of the real term 2ρG r λ 2 /t, and the imaginary Hanle term i(λ/λ m ) 2 originating from the applied field. While the former leads to a reduction of λ due to the torque exerted by the NM/FMI interface to the spins [30,32], the latter causes, in addition, the precession of the spins when the s and H are noncollinear [40].…”

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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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“…To overcome this problem, a spin-selective resistive contact such as an insulating barrier (I) can be inserted between the FM and NM (i.e., FM/I/NM), which dramatically increases the spin accumulation and hence the spin injection efficiency. Recently, Fukuma et al reported 15 giant enhancement of spin accumulation in NiFe/MgO/Ag lateral spin valves, where MgO reduces the spin resistivity mismatch between NiFe and Ag. A DSV analog of such a device can be produced by incorporating two insulating barriers on both sides of the middle ferromagnet, i.e., the FM1/NM/I/FM2/I/NM/FM1 junction.…”

Section: Discussionmentioning

confidence: 99%

Band-structure-dependent nonlinear giant magnetoresistance in Ni1−xFexdual spin valves

et al. 2012

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Conventional giant magnetoresistance (GMR) in spin valves is current-independent, so the resistance of a device depends only on the relative orientation of the magnetic layers. In dual spin valves consisting of three ferromagnetic (FM) layers separated by nonmagnetic (NM) spacers (i.e., a FM1/NM/FM2/NM/FM1), GMR can be currentdependent if spin can accumulate in FM2 when outer FM1 layers are aligned antiparallel. Currently the underlying physics is poorly understood, although spin accumulation in FM2 is likely to depend on the gradient in the density of states at the Fermi energy of the ferromagnet. To investigate this hypothesis, we have measured a series of dual spin valves with Ni 1−x Fe x as FM2 layers of varying composition. We show that both the magnitude and sign of the nonlinear GMR depend strongly on the Fe content and thus on the band structure of the ferromagnet FM2.

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Giant enhancement of spin accumulation and long-distance spin precession in metallic lateral spin valves

Cited by 180 publications

References 40 publications

Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes

Gate-tunable black phosphorus spin valve with nanosecond spin lifetimes

Modulation of pure spin currents with a ferromagnetic insulator

Band-structure-dependent nonlinear giant magnetoresistance in Ni1−xFexdual spin valves

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