Highly Spin-Polarized Room-Temperature Tunnel Injector for Semiconductor Spintronics using MgO(100)

Solid State and Photonics Laboratory, Stanford University, Palo Alto, California, United States
Physical Review Letters (Impact Factor: 7.51). 03/2005; 94(5):056601. DOI: 10.1103/PhysRevLett.94.056601
Source: PubMed


The spin polarization of current injected into GaAs from a CoFe/MgO(100) tunnel injector is inferred from the electroluminescence polarization from GaAs/AlGaAs quantum well detectors. The polarization reaches 57% at 100 K and 47% at 290 K in a 5 T perpendicular magnetic field. Taking into account the field dependence of the luminescence polarization, the spin injection efficiency is at least 52% at 100 K, and 32% at 290 K. We find a nonmonotonic temperature dependence of the polarization which can be attributed to spin relaxation in the quantum well detectors.

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    • "The first one is to use a quarter-wave plate. The second possibility is based on the electrical injection of spin-polarized carriers into the active region [1] [2] [3] [4] [5] [6]. The third possibility is to modify the local electromagnetic field, for example, using chiral liquid crystals [7] [8] [9]. "
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    Optics Letters 12/2014; 40(7). DOI:10.1364/OL.40.001528 · 3.29 Impact Factor
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    • "For samples capped with Au and at 7.1 to 28 ML, the uniaxial anisotropy is clearly visible and coexists with a four-fold cubic magnetocrystalline anisotropy. Its global easy axis is along [0] [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] while [010] and [001] directions are equally magnetic hard. Such orientation of the easy and hard axes can also be found in the MgO capped samples within the same range. "
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    ABSTRACT: Magnetic anisotropies of Fe/MgO/GaAs(100) hybrid structure with two different nonmagnetic capping materials, Au and MgO have been studied by ferromagnetic resonance (FMR). A uniaxial anisotropy, unexpected from the crystal structure was observed in the ultrathin films for both capping materials. Its global easy axis is along [0-11] direction while two (010) directions are equally magnetic hard regardless of the overlayer material. The in-plane uniaxial anisotropy (in-plane cubic anisotropy) of the Au capped samples is stronger (weaker) than that of the MgO capped ones within the range of t <sub>Fe</sub> = 7.1 to 28 ML. This suggests that the MgO overlayer suppresses the uniaxial anisotropy faster than the Au overlayer.
    IEEE Transactions on Magnetics 12/2008; 44(11-44):2907 - 2910. DOI:10.1109/TMAG.2008.2002195 · 1.39 Impact Factor
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    • "There are two big challenges in the realization of a spin-FET [2]: (i) efficient spin-polarized current injection, and (ii) spin-dependent conductance modulation by the applied electric field. In spite of the constant progress in the spin-polarized carrier injection technique [8] [9], the efficiency it is still far from 100%. In turn, the modulation of the spin polarized current is pretty low (about several percent) [10]. "
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