Authors: B.K. Kuanr, R.L. Marson, S.R. Mishra
Affilation: University of Colorado at Colorado Springs, United States
Pages: 146 - 149
Keywords: nickel nanowires, Isolator, band-stop filter, microwave device
Transition metals and their alloys have magnetic properties suitable for electronic applications, especially in the microwave range, such as circulators, isolators and filters. Arrays of Ni nanowires were electrodeposited into alumina oxide templates with various lengths (11-50 micron) and fixed pore diameter (150 nm). The use of nanowires as a tunable stop-band notch-filter (reciprocal device) in a coplanar waveguide geometry has been assessed. The stop-band frequency (fr) is observed to be tunable up to 24 GHz with an applied field (H) of up to 6 kOe. Microwave resonance-isolators (non-reciprocal device) are realized and measured by a vector network analyzer and a micro-probing system. Results on transmission coefficients show a non reciprocal effect, which reaches 6 dB/cm at 24 GHz. The performance of broadband isolators can be characterized by the ratio fmax /fmin, where fmin and fmax are defined as the edges of the frequency band in which the devices have acceptable operating characteristics. For the most advanced isolators available today this ratio is approximately 3:1. This investigation presents how to improve broadband performance substantially. Further, the magnetization behavior of these nanowires were investigated with ferromagnetic resonance (FMR) techniques; fixed frequency (conventional FMR) and swept frequency (Network Analyzer FMR). Both resonance spectra indicate the presence of strong dipolar interaction between the nanowires. The fundamental magnetic parameters like spontaneous magnetization, gyromagnetic ratio, and magnetic anisotropies of the nanowires were derived from the angular variation of resonance field data to FMR relation.