Multiferroic Behavior in Composites of Nickel-Exchanged Glass Containing Nanoparticles of Barium Titanate

A multiferroic material has been synthesized by first growing BaTiO3 nanocrystals in a silica glass and then subjecting the composite to a two‐stage ion‐exchange reaction of the type Ti4+↔2Ni2+. The nanocomposite retained the usual ferroelectric characteristics with lower values of the dielectric constant and remanent polarization. It also showed ferromagnetic hysteresis at temperatures in the range 10–300 K. At temperatures below ∼10 K, the magnetization exhibited a sharp increase as the temperature was reduced. This has been explained on the basis of a one‐dimensional Heisenberg ferromagnet consisting of Ni2+ ions at the surfaces of the nanocrystals. The nanocomposite showed magnetodielectric coupling at room temperature. The dielectric constant increased as a function of magnetic field, showing a maximum at 4 kOe. This has been ascribed to magnetostriction of the new BaTiO3 nanocrystalline phase.