Magnetic susceptibilities of diluted magnetic semiconductors and anomalous Hall-voltage noise

TL;DR

This paper develops a semiclassical theory for spin dynamics and susceptibilities in diluted magnetic semiconductors, revealing how spin-orbit coupling affects diffusion and magnetic transition temperatures, and predicts enhanced Hall-voltage noise near the Curie point.

Contribution

It introduces a comprehensive semiclassical framework for spin and charge dynamics in doped semiconductors with magnetic impurities, including anisotropic diffusion and noise predictions.

Findings

Spin susceptibilities are derived for various doping types.

Spin-orbit coupling causes anisotropic diffusion and lowers Curie temperature.

Hall-voltage noise is significantly enhanced near the Curie temperature.

Abstract

The carrier spin and impurity spin densities in diluted magnetic semiconductors are considered using a semiclassical approach. Equations of motions for the spin densities and the carrier spin current density in the paramagnetic phase are derived, exhibiting their coupled diffusive dynamics. The dynamical spin susceptibilities are obtained from these equations. The theory holds for p-type and n-type semiconductors doped with magnetic ions of arbitrary spin quantum number. Spin-orbit coupling in the valence band is shown to lead to anisotropic spin diffusion and to a suppression of the Curie temperature in p-type materials. As an application we derive the Hall-voltage noise in the paramagnetic phase. This quantity is critically enhanced close to the Curie temperature due to the contribution from the anomalous Hall effect.