Spin transport and accumulation in <i>n</i>+-Si using Heusler compound Co2FeSi/MgO tunnel contacts

Ishikawa, M.; Sugiyama, H.; Inokuchi, T.; Hamaya, Kohei; Saito, Y.

doi:10.1063/1.4929888

Cited by 23 publications

(26 citation statements)

References 27 publications

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“…For instance, in two-terminal magnetoresistance devices having two ferromagnetic contacts on a nonmagnetic channel, the current is applied between the two ferromagnetic contacts and the spin signal is obtained from the two-terminal voltage between the two contacts. Importantly, for devices in which the spin detector contact is biased, the observed spin signals are surprising and puzzling [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] , and no suitable explanation for the peculiar behavior is available. Moreover, when existing (linear) transport theories are applied to devices with a biased detector, the conclusions are inconsistent with those obtained from analysis of nonlocal spin transport devices, even if the same structure is used for the different measurement configurations.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Electrical Spin Conversion in a Biased Ferromagnetic Tunnel Contact

et al. 2018

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The conversion of spin information into electrical signals is indispensable for spintronic technologies. Spin-to-charge conversion in ferromagnetic tunnel contacts is well-described using linear (spin-)transport equations, provided that there is no applied bias, as in nonlocal spin detection. It is shown here that in a biased ferromagnetic tunnel contact, spin detection is strongly nonlinear. As a result, the spin-detection efficiency is not equal to the tunnel spin polarization. In silicon-based 4-terminal spin-transport devices, even a small bias (tens of mV) across the Fe/MgO detector contact enhances the spin-detection efficiency to values up to 140 % (spin extraction bias) or, for spin injection bias, reduces it to almost zero, while, parenthetically, the charge current remains highly spin polarized. Calculations reveal that the nonlinearity originates from the energy dispersion of the tunnel transmission and the resulting nonuniform energy distribution of the tunnel current, offering a route to engineer spin conversion. Taking nonlinear spin detection into account is also shown to explain a multitude of peculiar and puzzling spin signals in structures with a biased detector, including two-and three-terminal devices, and provides a unified, consistent and quantitative description of spin signals in devices with a biased and unbiased detector.

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Section: Introductionmentioning

confidence: 99%

Nonlinear Electrical Spin Conversion in a Biased Ferromagnetic Tunnel Contact

et al. 2018

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“…3 [48] which is so called the donordriven spin relaxation. We have experimentally clarified that the spin relaxation mechanism at low temperatures in degenerate Si [23] and Ge [28,29] cannot quantitatively be interpreted in terms of the Elliott-Yafet mechanism but the mechanism due to the impurity-and phonon-induced intervalley spin-flip scattering. Using their theory, [48] we can tentatively discuss the spin lifetime in the degenerate SiGe layers.…”

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confidence: 99%

Pure spin current transport in a SiGe alloy

Naitô

Yamada

Tsukahara

et al. 2018

Appl. Phys. Express

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Using four-terminal nonlocal magnetoresistance measurements in lateral spin-valve devices with Si0.1Ge0.9, we study pure spin current transport in a degenerate SiGe alloy (n ∼ 5.0 × 10 18 cm −3 ). Clear nonlocal spin-valve signals and Hanle-effect curves, indicating generation, transport, and detection of pure spin currents, are observed. The spin diffusion length and spin lifetime of the Si0.1Ge0.9 layer at low temperatures are reliably estimated to be ∼0.5 µm and ∼0.2 ns, respectively. This study demonstrates the possibility of exploring physics and developing spintronic applications using SiGe alloys.

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“…Theory shows that the higher-resistance semiconductor significantly depolarises the spin current from the ferromagnet unless the current is initially completely spin polarised. Several approaches have been taken to overcome this problem, including injection of electrons into the conduction band [9], introduction of a tunnel contact between the semiconductor and ferromagnet [10], and replacing the magnetic metals with a Heusler alloy [11,12]. Another approach is to use a semiconductor to generate the spin-polarised current [13].…”

Section: Introductionmentioning

confidence: 99%

Spin- and angle-resolved photoemission studies of the electronic structure of Si(110)“ 16×2 ” surfaces

et al. 2019

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The electronic structure of Si(110)"16 × 2" double-domain, single-domain and 1 × 1 surfaces have been investigated using spin-and angle-resolved photoemission at sample temperatures of 77 K and 300 K. Angle-resolved photoemission was conducted using horizontally-and vertically-polarised 60 eV and 80 eV photons. Band-dispersion maps revealed four surface states (S1 to S4) which were assigned to silicon dangling bonds on the basis of measured binding energies and photoemission intensity changes between horizontal and vertical light polarisations. Three surface states (S1, S2 and S4), observed in the Si(110)"16 × 2" reconstruction, were assigned to Si adatoms and Si atoms present at the edges of the corrugated terrace structure. Only one of the four surface states, S3, was observed in both the Si(110)"16 × 2" and 1 × 1 band maps and consequently attributed to the pervasive Si zigzag chains that are components of both the Si(110)"16 × 2" and 1 × 1 surfaces. A state in the bulk-band region was attributed to an in-plane bond. All data were consistent with the adatom-buckling model of the Si(110)"16 × 2" surface. Whilst room temperature measurements of Py and Pz were statistically compatible with zero, Px measurements of the enantiomorphic A-type and B-type Si(110)"16 × 2" surfaces gave small average polarisations of around 1.5% that were opposite in sign. Further measurements at 77 K on A-type Si(110)"16 × 2" surface gave a smaller value of +0.3%. An upper limit of ∼ 1% may thus be taken for the longitudinal polarisation.

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Spin transport and accumulation in n+-Si using Heusler compound Co2FeSi/MgO tunnel contacts

Cited by 23 publications

References 27 publications

Nonlinear Electrical Spin Conversion in a Biased Ferromagnetic Tunnel Contact

Nonlinear Electrical Spin Conversion in a Biased Ferromagnetic Tunnel Contact

Pure spin current transport in a SiGe alloy

Spin- and angle-resolved photoemission studies of the electronic structure of Si(110)“ 16×2 ” surfaces

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