Electrically driven magnetization of diluted magnetic semiconductors actuated by Overhauser effect

TL;DR

This paper proposes a method to control the magnetization of diluted magnetic semiconductors using quasi-Fermi level splitting, mimicking an external magnetic field, without changing hole density, based on Overhauser effect physics.

Contribution

It introduces a novel approach to manipulate DMS magnetization via quasi-Fermi level splitting, extending the Overhauser effect to semiconductor spintronics.

Findings

A 0.1 meV quasi-Fermi level splitting can mimic a 1 T magnetic field.

Magnetization control is achievable without altering hole density.

The proposed effect can be demonstrated using a lateral spin-valve structure.

Abstract

It is well-known that the Curie temperature, and hence the magnetization, in diluted magnetic semiconductor (DMS) like Ga$_{1-x}$Mn$_x$As can be controlled by changing the equilibrium density of holes in the material. Here, we propose that even with a constant hole density, large changes in the magnetization can be obtained with a relatively small imbalance in the quasi-Fermi levels for up-spin and down-spin electrons. We show, by coupling mean field theory of diluted magnetic semiconductor ferromagnetism with master equations governing the Mn spin-dynamics, that a mere splitting of the up-spin and down-spin quasi-Fermi levels by 0.1 meV will produce the effect of an external magnetic field as large as 1 T as long as the alternative relaxation paths for Mn spins (i.e. spin-lattice relaxation) can be neglected. The physics is similar to the classic Overhauser effect, also called the dynamic nuclear polarization, with the Mn impurities playing the role of the nucleus. We propose that a lateral spin-valve structure in anti-parallel configuration with a DMS as the channel can be used to demonstrate this effect as quasi-Fermi level splitting of such magnitude, inside the channel of similar systems, have already been experimentally demonstrated to produce polarization of paramagnetic impurity spins.