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Since the eddy-current problem usually depends on the geometry of the moving conductive sheet and the pole shape, there is no general method for solving it analytically. This paper presents a method for analysis of the eddy current in the special case of a rotating disk in a time-invariant field. The analysis uses Coulomb's law and the method of images to consider the boundary conditions. First, the surface charge generated in the rotating disk is obtained and Coulomb's law is applied to calculate the electric field intensity, assuming an infinite disk radius. Second, the finite disk radius is taken into account by introducing an imaginary electric field intensity to satisfy the boundary condition that the radial component of the eddy current is zero at the edge of the rotating disk. Third, the braking torque is calculated by applying the Lorentz force law. The paper compares the computed braking torque with the experimental results to establish the validity of the model. Index Terms--Coulomb's law, eddy-current brake (ECB), eddy-current distribution, image method, mapping.

Motivated by reports of the effect of ion irradiation on the magnetic properties of thin films, this paper outlines a new and possibly advantageous method of patterning magnetic antidot-type arrays by changing the magnetic properties of thin-film NiFe through [Ga.sup.+] implantation rather than by removal of material. Studies of conventional antidot arrays have reported regular remenant states of interest as possible stored bits trapped during hard axis magnetization reversal. In this paper, we report a study of [Ga.sup.+] implanted antidot-type arrays, which also support remanent states during hard and easy axis magnetization reversal. The energetics of the implanted antidot-type array system are considered, and the reason for the different magnetization reversal process in comparison with conventional antidot arrays is speculated to be due to the energy associated with the increased coercivity and domain wall pinning at implantation-induced damage sites. Index Terms--Antidot array, FIB Ga implantation, Lorentz microscopy, patterned media.

A study was conducted to analyze the magnetization distributions of an array of small NiFe elements. Lorentz transmission electron microscopy and magnetic force microscopy were utilized to carry out the analysis. The samples were made using electron beam lithography and lift-off patterning on electron transparent Si3Ni4 membrane substrates. Experimental results indicated different facets of the magnetization distributions on soft magnetic thin films.