Size dependent microwave properties of ferrite nanoparticles: Application to microwave devices

We studied the magnetic field dependence of the resonance frequency (f(r)) and frequency linewidth (Delta f) of iron oxide nanoparticles (Fe(3)O(4)) with different particle sizes spin-coated on a coplanar waveguide. Using a vector network analyzer, we find that the resonance frequency increases with an increase in applied field for all particle sizes, while Delta f decreases with the increase in the particle size. We have also carried out a theoretical study using the power absorbed by the different regions of the coplanar waveguide and found that the results are in accordance with the experiment. (c) 2009 American Institute of Physics. [DOI: 10.1063/1.3073836]