Hyperfine Interactions and Spin Transport in Ferromagnet-Semiconductor Heterostructures

TL;DR

This paper investigates hyperfine interactions and spin transport in Fe/GaAs heterostructures, revealing how nuclear polarization affects electron spin dynamics and enabling electrical detection of nuclear magnetic resonance.

Contribution

It introduces a coupled drift-diffusion model that accounts for hyperfine interactions, allowing independent determination of electron spin polarization in ferromagnet-semiconductor devices.

Findings

Nuclear polarization influences electron spin signals significantly.

The model accurately predicts the dependence of spin signals on bias and magnetic field.

Electrical detection of nuclear magnetic resonance is demonstrated.

Abstract

Measurements and modeling of electron spin transport and dynamics are used to characterize hyperfine interactions in Fe/GaAs devices with $n$-GaAs channels. Ga and As nuclei are polarized by electrically injected electron spins, and the nuclear polarization is detected indirectly through the depolarization of electron spins in the hyperfine field. The dependence of the electron spin signal on injector bias and applied field direction is modeled by a coupled drift-diffusion equation, including effective fields from both the electronic and nuclear polarizations. This approach is used to determine the electron spin polarization independently of the assumptions made in standard transport measurements. The extreme sensitivity of the electron spin dynamics to the nuclear spin polarization also facilitates the electrical detection of nuclear magnetic resonance.