Microwave properties of nanostructured magnetic materials

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The engineering of electromagnetic (EM) properties in materials is an important challenge in many areas of modern technology. Our research program aims to design, develop and characterize artificially nanostructured materials, with tailorable EM properties. The focus is on the microwave range of the spectrum. The EM response is governed by the impedance and dispersion relations and can be generally controlled by adjusting of the effective permeability, permittivity and conductivity of materials. By combining metallic and ferromagnetic nanoinclusions in a dielectric or a semiconducting matrix, we can exploit various charge and spin transport phenomena, along with spin and charge density waves, to achieve magnetic and dielectric responses not found in nature. This could lead to the possible demonstration of the first field-tunable left-handed metamaterials. This proposal is mainly concerned with arrays of ferromagnetic nanowires electroplated in nanoporous alumina membranes. The funds requested are essentially for the financial support of students. The specific objectives are: (1) to demonstrate the existence of artificial materials with significant magnetic and dielectric dispersions over the same microwave frequency range and controllable by an external magnetic field, (2) to understand the dissipation mechanisms limiting practical applications in such materials and to explore different avenues to minimize and compensate them, (3) to establish the conditions for effective magnetic wave propagation in the materials. In addition to magnetic nanowire systems, other materials studied include ferromagnetic nanoclusters embedded in III-V semiconductor epilayers, multiferroic thin films and films of carbon nanotubes. Outcomes of the work include: new tailorable low-loss materials and new design possibilities for microwave circuits (wireless technologies), and technologically relevant semiconductors with magnetic functionalities above room temperature, providing functional bridge between high speed electronic and optoelectronics.