Magnetoelectric coupling and overall properties of multiferroic composites with 0-0 and 1-1 connectivity

Magnetoelectric coupling in a multiferroic composite consisting of piezoelectric and piezomagnetic phases with 0-0 and 1-1 connectivity is not a commonly studied subject. Unlike 0-3, 1-3, and 2-2 connectivity, both constituent phases now exist on equal geometrical footing and the computational process to the solution of the effective properties is highly nonlinear. In this article we develop a micro-continuum theory to examine the magnetoelectric coupling coefficients, alpha(33) and alpha(11), for these two types of connectivity, and compare the results with the more commonly studied 0-3 and 1-3 composites. With the BaTiO3-CoFe2O4 (BTO-CFO) system, our study reveals that, with 0-0 connectivity, its alpha(33) and alpha(11) are substantially higher than those of 0-3 connectivity over a wide range of phase concentration, but that, with 1-1 connectivity, its alpha(33) is only comparable to that of the 1-3 composite whereas its alpha(11) is higher only within the range of 0.4-0.65 CFO vol. %. We have also calculated the remaining 15 independent material constants of the transversely isotropic multiferroic composite, including the 2 electric, 2 magnetic, 3 piezoelectric, 3 piezomagnetic, and 5 elastic constants, and found that most of these constants lie between those of the 0-3 and 1-3 composites with the CFO-in-BTO and BTO-in-CFO configurations. The influence of an imperfect interface is also studied for all 17 constants, with results found to be lower for most cases. These remarkable features signify the importance of phase connectivity and interface condition on magnetoelectric coupling and overall properties of a multiferroic composite. (C) 2015 AIP Publishing LLC.