Theoretical Investigation of effect of cobalt doping on properties of Iron Oxide by ADF *Robina Ashraf 1) , Saira Riaz 2) and Shahzad Naseem 3) Centre of Excellence in Solid State Physics, University of the Punjab, Lahore, Pakistan robina_ashraf85@yahoo.com ABSTRACT Iron Oxide has gained much interest in biomedical and spintronics applications due to its unique and novel properties. Amsterdam density functional (ADF) software is used for the first time in order to theoretically investigate the structural properties of cobalt doped iron oxide at 0K. TZ2P is used as basis set. Using GGA geometry optimization was achieved to observe structural properties. Inverse spinel cubic structure with lattice parameter of 8.39 Å is confirmed after geometry optimization by using GGA. 2X1X1 super cell of cobalt doped iron oxide is formed and GGA:PBE method is used to obtain total density of states (DOS) along with partial DOS of iron, cobalt and oxygen, respectively. Increase in band gap energy at 0K is observed after applying Hubbard potential (U=3 and 4 eV) for cobalt and iron, respectively. 1. INTRODUCTION Iron oxide has gained much interest of the researchers due to its existence in three most widely used stoichiometric phases (Fe 3 O 4 (magnetite), γ-Fe 2 O 3 (maghemite) and α-Fe2O3 (hematite)) (Riaz et al. 2014a). Depending on the presence of iron oxide in such unique and novel phases it is widely used in various fields like in biomedical (Riaz et al. 2014b, Riaz et al. 2012a) and spintronics (Riaz et al. 2013). Among them magnetite possesses crystal structure of cubic invers spinel with general formula AB 2 X 4 . X is a divalent anion while A and B are divalent cation and trivalent cation, respectively. In this stoichiometric formula of spinel ferrites tellurides, oxides and sulfides are mostly used (Hou et al. 2010). In case of maghemite, cubic close-packed arrangement is formed by oxygen ions and divalent iron cations occupy the octahedral sites, whereas trivalent iron cations have arbitrarily distributed on octahedral and tetrahedral sites. Hence, in magnetite, the presence of Fe +3 and Fe +2 cations make its structure complicated (Riaz et al. 2014b, Riaz et al. 2013). With the doping of cobalt in magnetite, CoFe 2 O 4 spinel ferrite is formed which has its 1) Graduate Student 2), 3) Professor