Magnetic and magnetoelectric properties of as-deposited and annealed BaTiO3–CoFe2O4 nanocomposite thin films

The magnetic and magnetoelectric (ME) properties of as-deposited and annealed BaTiO3–CoFe2O4 nanocomposite films with CoFe2O4 (CFO) nano-rods embedded in a BaTiO3 matrix have been studied and compared. The BaTiO3 phase in the as-deposited film changed from (0 0 1) preferred orientation to (1 0 0) orientation after annealing at 950 °C for 2 h. In the meantime, the magnetization increased dramatically from 200 to 380 emu cm−3. Distinct changes in magnetic contrast of the CFO nano-rods were observed by magnetic force microscopy under application of an electric field to the composite film. ME voltage coefficient as large as 4.9 × 10−9 s m−1 or 1.2 V Oe−1 cm−1 was estimated for the annealed film under 10 MV m−1, although the value was much lower for the as-deposited film. It is shown that higher ME effects can be found in films with good phase homogeneity, poly-domains and unrelaxed stress.