  Frequency dependant complex magnetic permeability is used to understand
RF-microwave behaviour of magnetic nanoparticles in the frequency range 250 MHz
to 3 GHz. The stable dispersions of Fe3O4 nanoparticles with mean size varying
between 11 to 16 nm are prepared for this purpose. The effect of mean particle
size and external static magnetic field over microwave absorption properties of
magnetic fluid is studied. It is observed that frequency of ferrimagnetic
resonance, frequency of maximum absorption, loss tangent and reflection loss
(RL) can be controlled by modifying mean particle size and strength of applied
external static magnetic field. This kind of study can be useful for
radio-microwave devices like tunable attenuator, EM sheilder, and other
applications like Hyperthermia.

Applied Physics;Soft Condensed Matter;Fluid Dynamics