Theoretical and experimental studies on the influence of Cr incorporation on the structural, optical, and magnetic properties of Bi0.5K0.5TiO3 materials

Multiferroic materials based on lead-free ferroelectric materials have potential applications in the fabrication of next-generation devices. Herein, the sol–gel method is used to synthesize pristine and Cr-doped Bi0.5K0.5TiO3 nanocrystals. Density functional theory simulation is performed to elucidate the mechanism underlying the observed electronic and magnetic properties of the nanocrystals. In materials doped with 9 mol% Cr, the substitution of Cr in the Ti site decreases the optical band gap from 3.09 eV to 2.26 eV and induces ferromagnetism at room temperature. The saturation magnetization of the materials is approximately 0.18 μB/Cr at 5 K and can be attributed to the interplay of the unpaired electron counts of Cr3+ ions in the crystal field mechanism and Jahn–Teller effect. Pristine Bi0.5K0.5TiO3 samples exhibit weak ferromagnetism at room temperature, given the existence of the mixed valence states of Ti4+ and Ti3+ and the formation of O or Ti vacancies during sample growth. The present study provides deep insight into the induction of magnetism in ferroelectric materials doped with transition metals. Such materials have potential spintronic applications.