Co Fe 2 O 4 – Ba Ti O 3 heterostructure was epitaxially grown on the (001)-SrTiO3 substrate via pulsed laser deposition, in which the bottom BaTiO3 layer epitaxially grown on the substrate acts as a buffer layer and effectively reduces the coherent constraint in the magnetic layer arising from the substrate. Microstructure studies from x-ray diffraction and electron microscopies showed good coherent epitaxy thin films of the (001)-CoFe2O4 and (001)-BaTiO3 on the substrate, which exhibits simultaneously strong ferroelectric and ferromagnetic responses. An obvious direct magnetoelectric coupling effect was observed in the thin films, which shows an enhancement compared to previous NiFe2O4–BaTiO3 heterostructures.

Bilayered heterostructures of ferrites and BaTiO3, epitaxially grown on SrTiO3 single crystal substrate via pulsed laser deposition, showed an obvious magnetoelectric effect. Employing such simple bilayered thin films as a prototype magnetoelectric read head was demonstrated. The media field from the bits in a magnetic recording medium was modeled by an ac magnetic field. The output voltage waveforms of the bilayered thin films well followed the wave functions of the ac magnetic excitation signal, which illustrates utility of the bilayered heterostructures as magnetoelectric read head.

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We fabricated epitaxial Co-doped BaTiO3 thin films (4–80nm thick) on Nb-doped SrTiO3 substrates. Our results indicate that Co ions exist in the form of Co3+ and that no Co metal clusters appear. All of the Co-doped BaTiO3 thin films show ferromagnetic behavior and the saturated magnetization increases as the film thickness decreases, which may be attributed to the effective exchange coupling interaction between oxygen vacancies and Co 3d spins. However, as the film thickness further decreases (∼4nm), the magnetization decreases, which may be mainly ascribed to surface effects.