Unified picture for diluted magnetic semiconductors

¹ Institut Néel, CNRS, département MCBT - 25 avenue des Martyrs, B.P. 166, F-38042 Grenoble Cedex 09, France, EU
² Jacobs University Bremen, School of Engineering and Science - Campus Ring 1, D-28759 Bremen, Germany, EU

^a richard.bouzerar@grenoble.cnrs.fr
^b georges.bouzerar@grenoble.cnrs.fr

Received: 7 September 2010
Accepted: 28 October 2010

Abstract

For already a decade the field of diluted magnetic semiconductors (DMS) has been one of the hottest. In spite of the great success of material-specific density functional theory (DFT) to provide accurately critical Curie temperatures (T_C) in various III-V–based materials, the ultimate search for a unifying model/theory is still an open issue. Many crucial questions are still without answer, as for example: Why, after one decade, does GaMnAs still exhibit the highest T_C? Is there any intrinsic limitations or any hope to reach room temperature? How to explain in a unique theory the proximity of GaMnAs to the metal-insulator transition, and the change from RKKY couplings in II-VI materials to the double-exchange regime in GaMnN? The aim of the present work is to provide this missing theory. We will show that the key parameter is the position of the Mn level acceptor and that GaMnAs has the highest T_C among III-V DMS. Our theory i) provides an overall understanding, ii) is quantitatively consistent with existing DFT-based studies, iii) is able to explain both transport and magnetic properties in a broad variety of DMS and iv) reproduces the T_C obtained from first-principle studies for many materials including both GaMnN and GaMnAs. The model also reproduces accurately recent experimental data of the optical conductivity of GaMnAs and predicts those of other materials.