  Magnetic, dielectric and calorimetric studies on 0.9BiFeO3-0.1BaTiO3 indicate
strong magnetoelectric coupling. XRD studies reveal a very remarkable change in
the rhombohedral distortion angle and a significant shift in the atomic
positions at the magnetic Tc due to an isostructural phase transition. The
calculated polarization using Rietveld refined atomic positions scales linearly
with magnetization. Our results provide the first unambiguous evidence for
magnetoelectric coupling of intrinsic multiferroic origin in a BiFeO3 based
system.
