Electron Spin Dynamics and Hyperfine Interactions in Fe/Al_0.1Ga_0.9As/GaAs Spin Injection Heterostructures

Abstract

We have studied hyperfine interactions between spin-polarized electrons and lattice nuclei in Al_0.1Ga_0.9As/GaAs quantum well (QW) heterostructures. The spin-polarized electrons are electrically injected into the semiconductor heterostructure from a metallic ferromagnet across a Schottky tunnel barrier. The spin-polarized electron current dynamically polarizes the nuclei in the QW, and the polarized nuclei in turn alter the electron spin dynamics. The steady-state electron spin is detected via the circular polarization of the emitted electroluminescence. The nuclear polarization and electron spin dynamics are accurately modeled using the formalism of optical orientation in GaAs. The nuclear spin polarization in the QW is found to depend strongly on the electron spin polarization in the QW, but only weakly on the electron density in the QW. We are able to observe nuclear magnetic resonance (NMR) at low applied magnetic fields on the order of a few hundred Oe by electrically modulating the spin injected into the QW. The electrically driven NMR demonstrates explicitly the existence of a Knight field felt by the nuclei due to the electron spin.

19 Figures - submitted to PRB

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Cited by in corpus (8)

• Electrical Detection of Spin Transport in Lateral Ferromagnet-Semiconductor Devices
• Spin relaxation in $n$-type GaAs quantum wells from a full microscopic approach
• Spin injection from perpendicular magnetized ferromagnetic $\delta$-MnGa into (Al,Ga)As heterostructures
• Hyperfine Interactions and Spin Transport in Ferromagnet-Semiconductor Heterostructures
• Electrical initialization of electron and nuclear spins in a single quantum dot at zero magnetic field
• Electrical Detection of Light Helicity using a Quantum Dots based Hybrid Device at Zero Magnetic Field
• Dynamic nuclear polarization at high Landau levels in a quantum point contact
• Generation of spin-polarized currents via cross-relaxation with dynamically pumped paramagnetic impurities