<title>Magnetoelectric effect in composite materials</title>

Abstract

Composites of piezoelectric and magnetostrictive materials show a product property called magnetoelectricity which is absent in its constituent phases. The electric and magnetic fields are linked in the composite through the elastic stress-strain fields of the piezoelectric and magnetostrictive phases. Thus an applied magnetic field causes electric polarization or an electric field applied across the composite causes magnetization in the composite material. Such materials are potentially useful as magnetoelectric transducers. In this work, we report the results of a theoretical and experimental investigation of ME composites of PZT-CoFe<SUB>2</SUB>O<SUB>4</SUB> and BaTiO<SUB>3</SUB>-CoFe<SUB>2</SUB>O<SUB>4</SUB> with various connectivities. The magnetically induced ME effect was measured by applying an ac magnetic field of 1 kHz frequency with a variable dc magnetic bias field. The maximum values of the ME voltage coefficient, were 92.8 (V/m)(kA/m) for the 2-2 CoFe<SUB>2</SUB>O<SUB>4</SUB>-PZT4 composites and 9.55 (V/m)(kA/m) for CoFe<SUB>2</SUB>O<SUB>4</SUB>-BaTiO<SUB>3</SUB> (20:80 mole %) ball mill mixed composites. Theoretical models were developed to calculate the ME voltage coefficient of 2-2 composites with different boundary conditions. Composites with 3-0 and 0-3 connectivities were modeled using a cubes model. The results show that the connectivities have a great effect on the magnetoelectric properties. An improvement of more than two orders of magnitude is possible by proper selection of materials and better process control to tailor the connectivity.