Microwave Properties of Magnetic Nanostructures
Advanced Materials Research Institute, University of New Orleans, New Orleans, LO
Date: January 18, 2008, Time: 3:30 pm, Location: W122-D3 Engineering Building 1, The University of Houston
Recent progress in computer technology and wireless communications stimulates research on new microwave materials. Arrays of magnetic nanostructures have been fabricated using electron beam writing followed by magnetron sputtering and lift-off technique. Ferromagnetic resonance is a sensitive method to measure magnetic anisotropy. Ferromagnetic resonance can be measured at a constant frequency using a resonant cavity method or in the field and frequency domains by the means of a vector network analyzer. Shape anisotropy of magnetic stripes and magnetostatic interactions of the stripes in the array can be used to tune ferromagnetic resonance fields. This effect can be utilized to design microwave filters and other microwave devices. Interesting microwave behavior was found in antidot arrays (perforated films). Two resonances controlled by the magnetostatic fields depend on the orientation of the applied field with respect to the array and merge when field is oriented along a diagonal of square holes. A reduced dimension of the nano-stripes results in multiple resonances. This effect is due to dimensional confinement of spinwaves form standing waves with their characteristic frequencies. Spinwaves or magnons are considered to be good candidates for quantum computing.