The coercive forces of hard magnets are calculated using one-layer defect model based on micromagnetism. The nucleation processes are classified into three types depending on the defect parameters. For certain values of the parameters, the nucleation field has a minimum value. The origin of the decreasing coercive force and a method of increasing the coercive force are also discussed.

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  Many papers have reported on Fe-N films, because of the material's high saturation magnetic flux density and permeability. However, there have been few studies of the read-write characteristics of this material. We have already drawn attention to the remarkably large head noise induced from this film in a single-pole head. To find a way of eliminating this disadvantage, we investigated the conditions of the deposition process. As a result, we found that the stress and the magnetostriction of films have to be controlled in order to suppress the head noise and to achieve high read-sensitivity. We also determined the optimum range of the stress and magnetostriction. Both high permeability and low head noise were obtained in the films deposited under these specific conditions. An improvement in the overwrite characteristics was also confirmed.

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  A fast simulation program is constructed that solves the Landau-Lifshitz--Gilbert equation and in which the demagnetizing field is derived from magnetic potentials within the magnetic substance. The Poisson and Laplace equations are solved iteratively to obtain the potentials. The initial values for iteration are predicted by using the values at previous time steps. The process of magnetization switching of square prism in the curling mode is simulated to demonstrate the validity and the capability of the program. The derived program is found to have a computing speed 20 times as fast as that of a similar program based on the conventional calculation of the demagnetizing field when the computing region consists of 30 × 30 cells.

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