Observation of room-temperature ferromagnetism in Co-doped Bi0.5K0.5TiO3 materials

We report the band gap modification and strong room ferromagnetism by substituting the Co ions for the Ti site of Bi0.5K0.5TiO3 materials. The predicted band gap of 2.11 eV and magnetic moment of 2.7 μB/Co are reproduced precisely in UV–Vis spectroscopy and superconducting quantum interference device experiments, respectively. We elucidate the driving mechanisms for these results in terms of the spin-exchange splitting between spin subbands in the presence of substitution ions and high-spin crystal field energy spectrum. This method would provide a promising approach to get single-phase multiferroics and resolve the problem of the scarcity of single-phase multiferroics in nature.