The goal of this project is to seek the strongest possible magnetoelectric coupling through the route of multiferroic composites that consist of a ferroelectric and a ferromagnetic phase. This idea grew out of the realization that single-phase multiferroic materials are rare, and among the existing ones their magnetoelectric coupling is generally weak. On the other hand a multiferroic composite could deliver strong magneto-electric interactions through their commonly shared mechanical characteristics. In this research, we will explore the maximum potential through a combination of micromechanics and phase-field approaches for both bulk and nanostructured multiferroic composites. We will apply the developed composite models to tune their volume concentrations, phase connectivity, and property contrast, to achieve this goal. The overall polarization of the composite under an external magnetic field, and its overall magnetization under an external electric field, will be determined to assess the magnetoelectric coupling. In this process the evolution of ferroelectric and magnetic domains will also be uncovered. We intend to consider BaTiO3-CoFe2O4 composites in great details, with the 1-3, 2-2, 0-3, and 3-3 connectivity for the bulk, and 1-3 and 2-2 for nanostructured thin films. In this way the maximum magnetoelectric coupling for each connectivity pattern, and for all patterns, can be quantified.
Multiferroic materials with strong magnetoelectric coupling have a wide range of applications that require the exchange and interaction of mechanical, electrical, and magnetic energies. In information storage, for instance, coupling allows the data to be written electronically and read magnetically, thus avoiding the need to create a high local magnetic field to write. This class of materials is also widely known to be useful as actuators, sensors, transducers, and high-frequency devices whose properties need to be tuned electrically or magnetically. In microelectronics, the on-chip integration also demands the use of many nano-scaled multiferroics. This work will have direct impact to the development of new high-end devices. We intend to use this opportunity to educate some high school and undergraduate and graduate students. The PI will establish a summer program with TARGET (The Academy at Rutgers for Girls in Engineering and Technology) to increase their awareness. He will enlist the motivated undergraduates to join the Honor J.J. Slade Scholar Program (which requires a thesis), and provide multidiscipline training to the graduate students with a new course, Mechanics of Multiferroic Materials, and a weekly seminar. Minority, women, and economically underprivileged students will be actively recruited. The results will be made open to the public through publications, lectures, and a website.
