Computer stimulations of particulate recording media

In order to further understand the behaviour of magnetic recording media the relationship between the microscopic and the macroscopic behaviour must be more precisely understood. Computer simulations are an invaluable tool in the development and testing of models of these media. Presented here are several computer simulations of particulate recording media, based on models of their microscopic behaviour. The simulations were used to probe the macroscopic behaviour of the systems and relate this to the microscopic models used. The four areas covered are: Time dependence in magnetic systems. A refinement of an established model of a perpendicular thin film. Results have been obtained for the logarithmic time dependence of the magnetisation together with the temperature dependence of both the remanent magnetisation and the viscosity coefficient. These all showed good agreement with previous work as did the results for the magnetisation decay of a small area of film. The linear transverse susceptibility of particulate recording media. Calculations have been made for a set of non-interacting Stoner-Wohlfarth particles. The introduction of both angular and magnitude distributions for the anisotropy yielded some very interesting results. Calculations were made for a range of differently textured systems. The results compare very favourably with some measurements obtained by industrial co-workers and explain some of the earlier results obtained by other workers. It is postulated that the transverse suscceptibility measurement may hold information about the magnetisation reversal mechanisms in these media. The effects of texture in the case of the FMR response. An established model was refined to include the effects of texture. Measurements were more closely simulated by adjusting of the texture to be more realistic. Results are shown comparing the measured response with the calculations. A related technique to the linear transverse susceptibility is developed in terms of a non-linear transverse susceptibility. Results of calculations suggest that this may be a useful singular point detection technique for obtaining anisotropy values. Further, since this technique has a high angular selectivity, it would probably be a useful tool in probing the texture of mat en a! s. A comparison between the linea.r transverse susceptibility and FMR responses is presented along with an overall discussion of the results obtained