Tuning magnetic properties of In₂O₃ by control of intrinsic defects

¹  Condensed Matter Theory Group, Department of Physics, Uppsala University - Box 530, S-751 21, Uppsala, Sweden, EU
²  Applied Materials Physics, Department of Materials Science and Engineering, Royal Institute of Technology S-100 44, Stockholm, Sweden, EU

Received: 21 August 2009
Accepted: 11 February 2010

Abstract

The electronic structure and magnetic properties of In₂O₃ with four kinds of intrinsic point defects (O vacancy, In interstitial, O interstitial, and In vacancy) have been theoretically studied using the density functional theory. The defect energy states of the O vacancy and In interstitial are close to the bottom of conduction band and act as shallow donors, while the defect energy states of the In vacancy and O interstitial are just above the top of the valence band and act as shallow acceptors. Without addition of any magnetic ions, all the hole states are completely spin polarized, while the electron states display no spin polarization. This implies that semiconducting In₂O₃ can display magnetic ordering, purely due to the intrinsic defects. However, the formation energies for neutral p-type defects are too high to be thermodynamically stable at reasonable temperatures. Nevertheless, it is shown that negative charging can greatly decrease the formation energies of p-type defects, simultaneously removing the local magnetic moments. We conlcude that V_In''' and O_I'' will be the dominant compensating defects as In₂O₃ is doped with TM ions, such as Sn, Mo, V and Cr. This result is consistent with the general view that the p-type defect is a key feature to mediate ferromagnetic coupling between transition metal ions of dilute concentration in metal oxides.