Dynamical Nuclear Polarization by Electrical Spin Injection in Ferromagnet-Semiconductor Heterostructures

TL;DR

This paper demonstrates electrical spin injection from Fe into AlGaAs heterostructures, revealing how internal magnetic fields and nuclear polarization influence spin dynamics, with implications for spintronic device control.

Contribution

It introduces a model that explains hysteresis in spin injection signals by incorporating magnetocrystalline anisotropy, spin relaxation, and nuclear polarization effects.

Findings

Spin injection observed in small magnetic fields (<500 Oe).

Internal magnetic fields depend on injection current density.

Hysteresis explained by a combined model of anisotropy, relaxation, and nuclear polarization.

Abstract

Electrical spin injection from Fe into Al$_x$Ga$_{1-x}$As quantum well heterostructures is demonstrated in small (< 500 Oe) in-plane magnetic fields. The measurement is sensitive only to the component of the spin that precesses about the internal magnetic field in the semiconductor. This field is much larger than the applied field and depends strongly on the injection current density. Details of the observed hysteresis in the spin injection signal are reproduced in a model that incorporates the magnetocrystalline anisotropy of the epitaxial Fe film, spin relaxation in the semiconductor, and the dynamical polarization of nuclei by the injected spins.