Yasushi Kanai

Resonant frequency analysis of reentrant resonant cavity applicator by using FEM and FD-TD method

A reentrant resonant cavity applicator is analyzed as a generalized eigenvalue problem by using the finite element method (FEM) with edge elements. The subspace iteration method is used to solve for selected eigenvalues. The resonant frequencies obtained are in good agreement with both the measured values and with the ones obtained using the finite-difference time-domain (FD-TD) method. Computation time and the amount of memory required are also discussed.

Further discussion on magnetic vector potential finite-element formulation for three-dimensional magnetostatic field analysis

A linear soft-iron and current model called the IEE Japan model using a novel vector potential finite-element formulation is examined. Calculated and measured results are in close agreement. For comparison, the same model was calculated by the conventional variational formulation. The divergence of magnetic vector potential equals zero at the boundary of different materials and the values themselves are small enough at the Gaussian quadratural points, which means that uniqueness of the solution is guaranteed. The gauge condition is determined by the formulation, not by the boundary conditions. The new formulation requires less computing time and memory than the conventional variational formulation. >

New formulation of finite-element method with gauge condition for three-dimensional magnetic field analysis

A novel magnetic vector potential formulation for three-dimensional problems is described. In order to establish the boundary conditions of different materials, it is necessary to impose some kind of gauge for three-dimensional magnetic field analysis. The partial differential equation including the gauge is discretized using the Galerkin method, which in turn yields a new formulation. The three components of A are formulated separately. By separating the components, memory size and calculation time are reduced greatly. The calculated results show that the formulation is valid. >

Modeling of magnetic recording heads for 2-D and 3-D finite element analysis

Modeling of magnetic recording heads using 2-D and 3-D finite element analysis was investigated for metal-in-gap and thin-film heads. It is confirmed that flux concentration as well as core thickness has to be carefully modeled when trying to solve in two dimensions. It is noted that nonlinear 2-D calculations of metal-in-gap heads are acceptable, however, 3-D analysis is strongly recommended for thin-film heads. >

Fast and stable non-linear converging method

In this paper, a non-linear converging method in the finite element analysis for magnetic field problems is proposed. Two types of materials with different saturation characteristics are considered. One has a gradual saturation characteristic called gradual saturaion, the other has a quick saturaion characteristic called quick saturation. A simple model, in which the value of magnetic flux density B for the applied magnetic field H can be evaluated analytically, is used for the numerical calculation. It is known that for materials with gradual saturation, the Newton-Raphson method is efficient for non-linear converging. For the materials with quick saturation there are some examples in which it does not work well. Conditions for the Newton-Raphson method to be applicable are studied both theoretically and numerically. A new, fast and stable iterative method with some sort of relaxation is proposed. Using some numerical examples, it is shown that the fast and stable convergence in the numerical analysis for material with gradual saturation and that with quick saturation is obtained.

Read-write characteristics of dual-sided metal-in-gap heads with various media

This paper describes the read-write characteristics of dual-sided metal-in-gap heads with various thin-film media. The relationship between calculated recording field gradient and measured linear recording density is also discussed. It is shown that a higher coercivity medium has a distinct advantage for obtaining higher linear density recordings. Experiments show that a D/sub 50/ of 64 kFCl is obtained by using a medium of H/sub c/=2150 [Oe]. However, it is found that D/sub 50/ is determined by the recording field gradient rather than the medium coercivity itself. An explicit relationship between recording field gradient and D/sub 50/ is also derived. >