Electronic structure of 3d-transition-metal monoxides: surface and bulk-point-defects D. K¨ odderitzsch a,∗ W. Hergert a Z. Szotek b W. M. Temmerman b a Fachbereich Physik, Martin-Luther-Universit¨ at Halle-Wittenberg, Friedemann-Bach-Platz 6, D-06099 Halle, Germany b Daresbury Laboratory, Warrington WA4 4AD, United Kingdom Abstract We discuss exchange coupling constants of a Heisenberg model in NiO and NiO(001), obtained with ab initio SIC- LSD method. In addition, using the same approach, we study vacancy induced half-metallicity in NiO and MnO. Key words: strongly correlated systems, oxide surfaces, vacancies, half metals PACS: 68.47.Gh, 71.27.+a, 75.30.Et, 73.20.-r, 75.70.Rf Transition-metal (TM) oxides are potential can- didates for spintronics applications, as they might give rise to high spin-polarisation [1]. For engineer- ing spintronics devices it is crucial to know the elec- tronic and magnetic structure of these materials at the quantum-mechanical level. Also, character- ization of properties at an atomic level is impor- tant for experimental interpretation or providing parameters for theoretical investigations. Due to strong correlations within the TM-d- electron states, local spin density (LSD) approx- imation to density-functional theory (DFT) is not able to yield an adequate description of these materials. Self-interaction corrected (SIC)-LSD, on the other hand, provides reasonable electronic structure of these materials [2,3]. Here we report on an application of SIC-LSD, in the supercell implementation, to study magnetic ∗ Corresponding author Email address: d.koedderitzsch@physik.uni-halle.de (D.K¨odderitzsch). interactions in NiO and NiO (001) [4]. In addition, we discuss the effect of low concentration of cation vacancies on the magnetic properties of such TM oxides as MnO and NiO [5]. The magnetic interactions in bulk TM oxides can be represented by an isotropic Heisenberg model with finite range interaction of localised classical spin moments residing on the TM-sites: H = - nn,nnn  ij J ij S i · S j , (1) including only nearest- (nn) and next nearest- neighbour (nnn) interactions (exchange coupling constants J b 1 and J 2 2 ). To extract the exchange constants we map the ab initio SIC-LSD total energies of different magnetic configurations onto the Heisenberg-model. For bulk NiO, SIC-LSD gives coupling constants of J b 1 = 1.8meV and J b 2 = -11meV which are in accord with the exper- imental values of J b 1 =0.7meV and J b 2 = -9.5meV Preprint submitted to Elsevier Science 1 July 2003