Recently, single-phase magnetoelectric (ME) hexaferrites have exhibited high ME coupling, α. As such, there appears to be potential to develop and fabricate novel devices based on the ME effect in various applications.
Composite magnetoelectric structure consisting of magnetostriction and piezoelectric layers mechanically attached to each other has been used in device developments for longer time. However, coupling the piezoelectric layer effectively to magnetostriction layer which needs physical attachment may be complicated in fabrication and sometimes challenging for integration purpose, besides most of this kind of devices needs a high DC voltage application for magnetostriction layer.
By evolution of ME single-phase hexaferrite materials operating at room temperature, we can take advantage of both types of transducers (electric and magnetic) in a single layer structure. That makes ME devices simpler and more straightforward for integration purposes. The ME effect implies that the application of a magnetic field, induces an electric Polarization, which can be measured by electric field in the ME layer and in the converse case applying an electric field/voltage, induces magnetization which can be detected by a pick-up coil in one way.
The objective is to utilize ME hexaferrites in new generation of devices compatible with CMOS for various device applications as E-field sensor, H-field sensor (for low frequency of biomedical measurements to higher frequencies of RF), as well as various tunable device applications such as tunable inductors and filters.
The focus was on exploring physical properties of single-phase hexaferrit-based devices by performing different experiments mostly from ~DC to ~10 MHz as well as higher GHz frequencies. While performing different experiment, ME device structures are developed step by step to serve as a platform for different application. Also, for the first time, thin films of ME hexaferrites were deposited successfully on silicon substrate to accommodate integration of these devices with CMOS technology.
To reduce the applied voltage to excite these materials, we have devised new technique by depositing of parallel conductive lines in the pane of film as well as depositing ME thin films on a conductive oxide layers. By these techniques we are able to reduce the excitation voltage as low as 1 V.
Finally a full monilitcally single-phase ME device on silicon substrate for H and E field sensing and tunabilty applications, single frequency detector, etc is designed, and the first prototype of such a device was successfully tested.
Advisor: Professor Carmine Vittoria
Professor Carol Livermore
Professor Fabrizio Lombardi