Possible magnetic-field-induced voltage and thermopower in diluted magnetic semiconductors

TL;DR

This paper predicts that in diluted magnetic semiconductors, magnetic-field gradients can induce voltage and thermopower effects due to carrier-magnetization coupling, with potential applications in spintronics.

Contribution

It introduces a theoretical framework predicting magnetic-field-induced voltage and thermopower in diluted magnetic semiconductors, including estimates for (Ga,Mn)As.

Findings

Magnetic-field gradients induce voltage in diluted magnetic semiconductors.

A large thermopower contribution is predicted from the same mechanism.

Predictions are valid for both uniform and stripe-like magnetization modulations.

Abstract

In diluted magnetic semiconductors, the carrier concentration and the magnetization of local moments are strongly coupled, since the magnetic interaction is mediated by the carriers. It is predicted that this coupling leads to an electric polarization due to an applied magnetic-field gradient and to the appearance of a magnetic-field-dependent voltage. An expression for this voltage is derived within Landau theory and its magnitude is estimated for (Ga,Mn)As. Furthermore, a large contribution to the thermopower based on the same mechanism is predicted. The role of fluctuations is also discussed. These predictions hold both if the magnetization is uniform and if it shows stripe-like modulations, which are possible at lower temperatures.