On the high-frequency measurement of the dynamic properties of nano-particle colloids

Abstract Measurement of the magnetic complex susceptibility, χ ( ω )= χ ′( ω )−i χ ″( ω ) by means of the transmission line technique, is a well established method for the determination of the dynamic properties of nano-particle colloids, such as magnetic fluids. From polarising studies one can obtain accurate data on the anisotropy constant, K , anisotropy field, H A , gyromagnetic constant γ , and the damping parameter, α . From data on χ ( ω ), one can determine the loss tangent, tan δ , of the samples and also a value of the precessional decay time, τ 0 . From polarized studies, one can investigate the presence of any hysteresis. The technique is also suitable for the investigation of the magnetic properties of composite samples. In this paper a review of the above mentioned topics are presented with examples of results obtained for a number of magnetic fluids.