THE FREQUENCY-DEPENDENCE OF THE COMPLEX SUSCEPTIBILITY OF MAGNETIC LIQUIDS

The frequency dependence of the magnetic susceptibility of kerosene or oil-based magnetic liquids has been measured. The volume fractions of particles range from 0.028 to 0.192. The liquids exhibit a broad maximum in the imaginary part at frequencies of the order of 10 MHz. There are no discernible effects of particle interactions in the values of the initial low-frequency susceptibility, which are practicaly constant up to 10(5) Hz, or in the height of the maximum. There are particle interactions manifesting themselves in the details of the shape of the susceptibility curves in the frequency region approaching the maximum. The observed dissipative behaviour is interpreted as a relaxation process in which single particles with a distribution of sizes change their magnetization direction by Neel rotation.