We demonstrate in a simple model the surprising result that turning on an on-site Coulomb interaction $U$ in a doped band insulator leads to the formation of a half-metallic state. In the undoped system, we show that increasing $U$ leads to a first order transition at a finite value $U_{\mathrm{AF}}$ between a paramagnetic band insulator and an antiferomagnetic Mott insulator. Upon doping, the system exhibits half-metallic ferrimagnetism over a wide range of doping and interaction strengths on either side of $U_{\mathrm{AF}}$. Our results, based on dynamical mean field theory, suggest a new route to half metallicity, and will hopefully motivate searches for new materials for spintronics.

• Received 23 July 2013

DOI:https://doi.org/10.1103/PhysRevLett.112.106406