ON THE INFLUENCE OF DISTRIBUTION-FUNCTIONS ON THE AFTER-EFFECT FUNCTION OF FERROFLUIDS

The after-effect function, F(t), or magnetization decay of a ferroflui d sample may be determined from frequency-dependent complex relative m agnetic susceptibility data of the sample. Here we report on the effec t that two distribution functions, namely the magnetic analogues of th e Cole-Cole and Frohlich distribution functions, have on the after-eff ect function of three ferrofluid samples. The samples chosen were thos e for which good alternating current susceptibility data, X'(omega) an d K''(omega), were available, namely in the lower frequency range in w hich the frequency of the maximum of X''(omega), f(max) is indicative of the presence of aggregates. However, because of a lack of knowledge of the sizes of these aggregates it was not possible to generate a di stribution function. By fitting the Cole-Core and Frohlich distributio n functions to the susceptibility data it is shown that the after-effe ct function is very sensitive to the distribution used, illustrating t he difficulty of determining accurate after-effect functions without a n adequate knowledge of the distribution function. it is shown that, i n all cases, the use of the Frohlich distribution function results in a decay function with the fastest initial rate of decay.