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The static states and reversal processes of write head are studied and compared by two micromagnetic models with sawtooth edges or smooth edges, respectively. In the calculation of magnetostatic interaction with smooth edges, the analytical expression of demagnetization matrix for right-angle triangular prism clusters at hypotenuse has been found. The static domain structures in the main pole tip of both models have a slight difference and differ a little more with higher exchange constant. The switching processes in the two models also have similar behavior, except when the down-track film thickness is less than the pole tip width. Both the exchange field and film thickness affect the ultimate magnetization perpendicular to media and the speed of reversal. Index Terms--Hard disk drive (HDD), micromagnetic, regular mesh, sawtooth edge, write head.

Thermal switching has been recognized as a possible limit to archival storage in advanced high density recording media . Thinner films with more isolated grains suffer from large magnetic viscosities [approximately]10%/decade. Previous work has shown that the observed remanent coercivity [H.sub.CR]([Tau]) in high viscosity tapes can be predicted from Sharrock's Law down to [10.sup.-9]s. Here we report high speed switching results on thin film media which show that the remanent coercivity at [10.sup.-8]s is increased [approximately]40 % relative to the VSM value in these films. A quantitative relationship between the viscosity, irreversible susceptibility, and the increase in [H.sub.CR)([Tau]) is demonstrated.

This paper treats the autonomous induction generator as a two-phase oscillator and compares it with another one, the very simple and well-known LC resonant circuit. As a result, an original explanation of the excitation process of the induction generator is presented. Furthermore, it is shown that the autonomous induction generator could be excited without capacitors by switching, in a suitable way, its resistive load in and out in the stator circuit. Index Terms - Autonomous excitation, induction generators, oscillators.

In this paper, we study the magnetization reversal process of single-domain Stoner--Wohlfarth particles subject to circularly polarized fields and short pulses using analytical and numerical models. We investigate the effect of short unipolar, bipolar field, and circularly polarized field pulses, which are applied perpendicular to the uniaxial magnetocrystalline anisotropy axis, on the magnetization switching dynamics. Index Terms--Fast switching, Landau--Lifshitz--Gilbert (LLG) equation, magnetization reversal.