On the significance of the area under the after-effect function curve of a magnetic fluid

The after-effect function, b(t), describes how the magnetization of a dissipative magnetic fluid decreases with time when a polarizing field, H, is suddenly removed. It is shown that with increasing H, the rate of decay of b(t) increases and also that the area, ∫^∞₀ b(t)dt=B, under each decay curve decreases. Here we investigate the significance of this and by means of a simple model, show that the normalized function, B/b(0), is in fact equal to the Debye relaxation time τ_D. The results of applying the model to theoretically generated data and also to data obtained from a magnetic fluid sample are presented