The objective of this research is to develop novel frequency agile reciprocal (tunable filters) and non-reciprocal (isolator and circulator) microwave devices based on stimuli-responsive magnetic nanowires composites. In the modern world when wireless connectivity guarantees to provide voice, video and data access to ?everyone, anywhere, and anytime? there is a constant need for remotely tunable microwave devices. The proposed research will integrate fabrication of magnetic nanowires, frequency agile microwave device design, characterization and modeling.
Intellectual Merit. For more than half a century the ferrites were the ?workhorse? of the microwave devices, especially for nonreciprocal applications. The main advantage of ferrites is the fact that they provide an extremely high electrical resistivity with reasonable good magnetic properties, which is very important at high frequencies view the eddy?current loss. However, their average magnetic properties impacts negatively the size and weight of ferrite based microwave devices. The stimuli-responsive magnetic nanowires composites will combine the advantages provided by superior electromagnetic properties of magnetic nanowires with the ability of the active polymer matrix to provide a remote tuning of these electromagnetic properties. Piezoelectric and light active polymers will be used to couple magnetic nanowires in planar structures. In the case of a piezoelectric matrix, an electric field applied across the device?s plane will determine a variation in its planar dimensions which will change the average distance between the magnetic nanowires. For light active polymers, besides a variation of the average interwire distance, a change in the angular texture of the wires can be triggered as the planarity of the polymer film changes under the action of an optical stimulus. Both of these coupling mechanisms between magnetic nanowires and stimuli responsive matrices will affect the frequency response of the composite material, as the ferromagnetic resonance frequency is strongly dependent on interwire interactions and orientation of the wires.
Broader Impact. The findings gained from this project will contribute to the basic understanding of the nanoscale physical phenomena, specifically nanomagnetism, providing insights into the dynamic properties of mesoscopic magnetic structures. The immediate benefit for the society comes from the big impact of the proposed activity on rf and microwave technologies. Also, this project will provide important training for graduate and undergraduate students in Physics, Chemistry and Nanomaterials Science. Students will be involved in all aspects of this program gaining important experience in processing and characterization of these materials. Further, this program will serve to expand nanotechnology education in Louisiana by exposing undergraduates students, especially minorities, to the latest research developments.
In the modern world when wireless connectivity guarantees to provide voice, video and data access to "everyone, anywhere, and anytime" there is a constant need for remotely tunable microwave devices. The objective of this research was to develop novel frequency agile reciprocal (tunable filters) and non-reciprocal (isolator and circulator) microwave devices based on stimuli-responsive magnetic nanowires composites. The proposed research integrated fabrication of magnetic nanowires with various configuration, frequency agile microwave device design, and characterization and modeling. Intellectual Merit. For more than half a century the ferrites were the "workhorse" of the microwave devices, especially for nonreciprocal applications. The main advantage of ferrites is the fact that they provide an extremely high electrical resistivity with reasonable good magnetic properties, which is very important at high frequencies view the eddy–current loss. However, their average magnetic properties impacts negatively the size and weight of ferrite based microwave devices. The stimuli-responsive magnetic nanowires composites combines the advantages provided by superior electromagnetic properties of magnetic nanowires with the ability of the active polymer matrix to provide a remote tuning of these electromagnetic properties. Piezoelectric and light active polymers were considered in this research project to couple magnetic nanowires in planar structures. The coupling between magnetic nanowires and stimuli responsive matrices affects the frequency response of the composite material. During this research project we developed several methods for the fabrication of arrays of magnetic nanowires, mainly using a template based method. As the quality of the templates can impact the properties of grown magnetic nanowires an important effort was devoted to designing and fabricating high quality templates. An example of alumina oxide (AAO) membrane we synthesized and used as a mold in fabrication of arrays of magnetic nanowires is shown in Fig. 1. High-quality arrays of magnetic nanowires with a good control of their morphology and configuration were accessible (See Fig. 1 and Fig. 2). A significant effort was devoted to integrate the magnetic nanowires in polymeric membranes. This process was achieved either by co-deposition of metal and polymer into the pores of an anodic alumina membrane or by replacing the AAO membrane of electrodeposited nanowires with a polymeric one. An example of the integration of polymeric membranes in sets of Ni nanowire is shown in Fig. 3. Extensive testing and measurements were carried out on the fabricated materials and structures, including structural, chemical and physical characterization. Magnetic and microwave measurements were carried out on the fabricated materials and structures. An example of the microwave response of sets of periodic magnetic nanowires fabricated by electron beam lithography is shown in Fig. 4. Broader Impact. The findings gained from this project contribute to the basic understanding of the nanoscale physical phenomena, specifically nanomagnetism, providing insights into the dynamic properties of mesoscopic magnetic structures. The immediate benefit for the society comes from the big impact of the proposed activity on rf and microwave technologies. Also, this project provided important training for graduate and undergraduate students in Physics, Chemistry and Nanomaterials Science. Two graduate students (one female) involved in all aspects of this program gained important experience in processing and characterization of these materials. Further, this program served to expand nanotechnology education in Louisiana by exposing 3 undergraduates students (one female), to the latest research developments.
