Effects of piezoelectric-phase orientations on magnetoelectric coefficient in AlN–FeCoSiB multiferroic composites

In this study, orientation dependences of ^ps₁₁′, ^ps₁₂′, ^pε₃₃′ and d₃₁′ for piezoelectric phase were investigated along arbitrary directions using relative experimental data and original matrices for AlN with point group of 6mm. Then, effects of various orientations of piezoelectric phase on magnetoelectric coefficient of AlN–FeCoSiB laminated multiferroic composites were studied. It was found that ^ps₁₁′ is a constant while ^ps₁₂′, ^pε₃₃′ and d₃₁′ exhibit high dependence on crystal orientations with their MAX values existing along [001]-axis. The magnetoelectric coefficient α_E33′ increases with decreased angle θ apart from c-axis of AlN in range of 90°–0°; the MAX α_E33′ = 5405 mV/cm Oe exists in AlN ∥ [001]—FeCoSiB. Along specific preferred orientations of piezoelectric phase, twofold–fivefold of enhancement of α_E33 can be obtained compared to randomly arranged composites. Volume fraction is found to be independent of orientations of component phases, and the volume fraction for magnetic phase f around 0.75 obtains the largest α_E33. The results suggest an approach of enhancing magnetoelectric coefficient of composite multiferroic materials through crystal-orientation controls of single crystals or textured ceramics.