Control of ferromagnetism via electron doping in In2O3:Cr

Carrier-induced ferromagnetism in wide-gap transparent conductive oxides has been widely discussed and debated, leading to confusion and skepticism regarding whether dilute magnetic oxides exist at all. We show from density-functional calculations within a band-gap corrected approach that ferromagnetic Cr-Cr coupling can be switched on and off via electron doping in the wide-gap transparent n-type conductive oxide In2O3. We show that (i) Cr does not produce in In2O3 any free electrons and renders the system an insulating paramagnet. (ii) Extrinsic n-type doping of In2O3:Cr via Sn produces free electrons, whose concentration is controllable via the oxygen partial pressure. Such additional carriers stabilize a strong long-range Cr-Cr ferromagnetic coupling.