Ab initio investigations in magnetic oxides

It is argued that band theory can be used as a valuable tool to investigate and model properties of several classes of oxide systems. This theoretical framework is presented in the first part of the article with details on the density functional theory (DFT) and its approximations leading to the local spin density functional LSDF as well as on the common methods built around it (mainly the augmented spherial wave ASW method used throughout this work). The major part of the article is devoted to case studies meant to illustrate the wealth and limits of the LSDF in addressing the electronic and magnetic structures of a selected variety of transition metal oxides of technological importance. Such systems are iron monoxide "FeO" (mainly the high pressure form), the archetype of half metallic ferro magnets CrO2, used in magnetic recording media, the simple and double perovskite derived systems: SrFeO3 and La2TIrO6 (T = Mn, Fe, Co) as well as manganese oxides (CaMnO3, Ca4Mn4O10 and Tl2Mn2O7) for which a giant magnetoresistive GMR behaviour was identified in recent years. The computed ground state magnetic configurations and electronic structure results are discussed and confrontations with experimental data are carried out when available. The chemical bonding properties are analysed, and a new conceptual approach is provided. (C) 2004 Elsevier Ltd. All rights reserved.