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 Bi 0.5 K 0.5 TiO 3 materials. The predicted band gap of 2.11 eV and magnetic moment of 2.7 μ B /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.