ON THE INFLUENCE OF INERTIAL EFFECTS, ARISING FROM ROTATIONAL BROWNIAN-MOTION, ON THE COMPLEX SUSCEPTIBILITY OF FERROFLUIDS

This paper reports on the use of the autocorrelation function of the magnetization decay of a ferrofluid to investigate the effects which the moment of inertia of single domain ferromagnetic particles have on the frequency dependent complex susceptibility, chi(omega)=chi'(omega)-(i) chi ''(omega), of ferrofluids. The contribution of particle inertial effects, arising from rotational Brownian motion, to an apparent resonance, indicated by the real component, chi'(omega), going negative at a frequency lower than that predicted by theory, is investigated. The Langevin treatment of Brownian motion is used to incorporate thermal agitation into the analysis.