Position: Ph.D. Candidate

Current Institution: Stanford University

Integration of Thin Film Magnetoelectric Composites for Voltage-Tunable Devices

Operation of today’s electronics is controlled by voltage and electric fields, not magnet fields. As a result, identifying methods for electrical control of magnetic devices has been a vibrant research topic in recent years. Magnetoelectric composites, combining piezoelectric materials and magnetostrictive materials, offer a unique and intriguing solution. In these composites, a voltage applied to the piezoelectric film causes both it and the adjacent magnetic film to strain. The magnetization of the magnetic material then responds to the strain accordingly and changes the operating state of the device. Bulk magnetoelectric composites have demonstrated large tunability of magnetic properties, magnetization rotation, or uniaxial magnetization switching under applied voltages. However, in order for these capabilities to be incorporated into electronic systems, magnetoelectric composites must be made into thin-film form and integrated with other silicon devices.

In this research work, we demonstrate integrated thin-film magnetoelectric composite resonant waveguide devices. The various materials and design considerations for producing these magnetoelectric devices will be discussed. Numerous materials were considered, however, in the end, the P96N4Z20T80 piezoelectric and Co43Fe43B14 magnetostrictive materials were selected for their high levels of strain control and linearity. In addition, the composite structure and electrode design trade-offs were simulated and optimized to produce maximal magnetoelectric coupling given the constraints of material thickness and the limitation of substrate clamping. Top and bottom interdigitated electrodes of the same voltage polarity were used to produce the most uniform in-plane, uniaxial tensile strain in the composite. Finally, tunability results for the resonant waveguides will be presented, illustrating the voltage control of the magnetization and relative permeability of the material in its thin-film form.

Amal El-Ghazaly recently completed her Ph.D. in Electrical Engineering from Stanford University under the direction of Professor Shan X. Wang and is currently pursuing postdoctoral research at the University of California Berkeley with Professor Jeffrey Bokor. Her postdoctoral work delves into understanding the mechanisms for ultrafast switching of magnetic dots both optically and electronically, and integrating these dots into a digital logic system. During her Ph.D., she was awarded the NSF graduate research fellowship, NDSEG research fellowship, and the Stanford DARE fellowship. Her doctoral work focused on the design and optimization of magnetic and magnetoelectric material composites for radio frequency devices. In the first part of her Ph.D., she demonstrated GHz-frequency range magnetic inductors and continued on to develop the first ever fully-integrated tunable RF waveguide resonator using thin film magnetoelectric composites. Dr. El-Ghazaly holds her Master’s and Bachelor’s degrees from
Carnegie Mellon University.