Electronic phase separation in insulating (Ga,Mn)As with low compensation: Super-paramagnetism and hopping conduction

TL;DR

This study investigates low compensated insulating (Ga,Mn)As, revealing electronic phase separation, super-paramagnetism, and hopping conduction, which explain the material's colossal magnetoresistance and magnetic behavior.

Contribution

It demonstrates disorder-induced electronic phase separation in (Ga,Mn)As with low Mn compensation, linking it to superparamagnetism and hopping conduction phenomena.

Findings

Variable-range hopping transport with Coulomb gap

Observation of super-paramagnetism rather than ferromagnetism

Colossal negative magnetoresistance below blocking temperature

Abstract

In the present work, low compensated insulating (Ga,Mn)As with 0.7% Mn is obtained by ion implantation combined with pulsed laser melting. The sample shows variable-range hopping transport behavior with a Coulomb gap in the vicinity of the Fermi energy, and the activation energy is reduced by an external magnetic field. A blocking super-paramagnetism is observed rather than ferromagnetism. Below the blocking temperature, the sample exhibits a colossal negative magnetoresistance. Our studies confirm that the disorder-induced electronic phase separation occurs in (Ga,Mn)As samples with a Mn concentration in the insulator-metal transition regime, and it can account for the observed superparamagnetism and the colossal magnetoresistance.