INVESTIGATION OF FERROMAGNETIC-RESONANCE IN MAGNETIC FLUIDS BY MEANS OF THE SHORT-CIRCUITED COAXIAL LINE TECHNIQUE

The short-circuit coaxial transmission line technique has been used to investigate ferromagnetic resonance in magnetic fluids over the frequ ency range 0.1-6 GHz. Measurements of the complex susceptibility, chi (omega) = chi'(omega) - i chi ''(omega), of magnetic fluid samples of magnetite and cobalt particles, of approximate median diameters 10 and 5.8 nm are presented. The presence of loss peaks in the chi ''(omega) components at approximate frequencies of 1.2 and 2.5 GHz, respectivel y, coupled with the transition of the chi'(omega) components from posi tive to negative values at slightly higher frequencies, is indicative of ferromagnetic resonance. Appropriate equations for the calculation of the complex susceptibility are presented.