Magnetodielectric coupling in core/shell BaTiO3/γ-Fe2O3 nanoparticles

We report an intriguing magnetodielectric coupling in BaTiO3/gamma-Fe2O3 dielectric core/ferrimagnetic shell nanoparticles. The dielectric constant steeply increases with magnetic field, and the frequency dependent magnetodielectric curve shows a resonancelike peak at high temperatures, while it decreases smoothly with field and no peak appears in the frequency dependent magnetodielectric curve at low temperatures. We attribute the observed magnetodielectric coupling to the Maxwell-Wagner effect combined with magnetoresistance at high temperatures and to possible spin-lattice coupling and its modification near interfaces at low temperatures. (C) 2007 American Institute of Physics.