The objective of this research is to fabricate and study magnetic tunnel junctions with an active multiferroic or ferroelectric barrier - termed magneto-electric tunnel junctions. Traditional magnetic tunnel junctions represent a class of device that utilizes the electronic spin for its performance. The proposed magneto-electric tunnel junctions are based on theoretical predictions that have identified asymmetry as a fundamental criterion for obtaining multi-functional devices. These devices are expected to exhibit simultaneous magneto-resistance and electro-resistance effects, coupled with subtle electronic transport effects. A comprehensive research program is planned which addresses issues related to the following components: sample fabrication, structural characterization, nanoscale magneto-electric properties, and device characterization. The basic focus of the proposed program will be on the investigation of magneto-electric transport properties of magneto-electric tunnel junctions with ultra-thin ferroelectric and multiferroic barriers and their composites.
The intellectual merit of the research lies in the investigation of novel heterostructures utilizing fundamental insight into electronic properties coupled with innovative fabrication and characterization methods that have the potential for realizing a new class of multiple-state resistance devices. State-of-the-art pulsed laser deposition techniques shall be used with unit-cell control to fabricate prototype devices. Device characteristics shall be investigated both at the nanoscale and global level. Nanoscale characterization would involve current-voltage characteristics of bilayer structures using conducting atomic force microscopy. Local ferroelectric switching properties of ultra-thin films shall be studied using piezoresponse force microscopy. Advanced scanning probe characterization investigating nanoscale ferroelectricity and tunneling properties shall be performed at the Center for Nanoscale Material Sciences at the Oak Ridge National Laboratory.
The Broader Impacts includes a multidisciplinary effort that will make significant contributions to scientific knowledge, education outreach and infrastructure. The scientific outcomes of the project are expected to include both advances in the fabrication of a new class of tunnel junction structures and fundamental understanding of their materials and physical characteristics. Device studies will provide a firm foundation for realizing multifunctional devices and, if successful, would have an extraordinary impact and open the door for a plethora of applications. The program will provide support for graduate and undergraduate students, including underrepresented minorities, and contribute to their broad interdisciplinary training. Project personnel will collaborate with local schools to facilitate participation by high school students in research.
