Orientation dependence of magnetoelectric coefficient in BaTiO3/CoFe2O4

Using the three-dimensional space coordinate transformation approach, orientation dependence of the longitudinal magnetoelectric coefficient αE33 in tetragonal BaTiO3/face centered cubic (fcc) CoFe2O4 composites was calculated in arbitrary directions. A clamp-free condition is used in the calculation. The direction along which αE33 is maximum is a function of psij, pεij, dij of piezoelectric phase and msij, mμij, qij of magnetostrictive phase referred to the crystallographic coordinate system. For a fixed CoFe2O4 orientation, the maximum αE33 lies along [001] axis of BaTiO3. And for a fixed BaTiO3 orientation, the maximum αE33 lies along [001] axis and a large αE33 also lies along [11l] (l > 0) of CoFe2O4. BaTiO3 || [001]/CoFe2O4 || [001] combination has the maximum αE33 which is 641 mV/cm Oe. The maximum αE33 is about 2 times of that of random orientated materials. Volume fraction is quite independent of orientation changes of both piezoelectric and magnetostrictive phases and the volume fraction for magnetostrictive phase f around 0.76 obtains the largest αE33. Our results suggest an approach of significantly enhancing magnetoelectric coefficient of composite multiferroic materials through crystal orientation and texture engineering.