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

Abstract

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. I.INTRODUC~ONIn designing magnetic recording heads, finite-element magnetic field analysis is one of the best tools for a better understanding of the various phenomena [l]. However, because of their complex structures and the presence of a gap, meshing is quite difficult and the number of elements becomes huge when trying to solve in three dimensions. Therefore, a 2-D calculation is often used, especially for ferrite Metal-In-Gap (MIG) heads. Instead of the finite element method, integral methods are sometimes used [2] since their meshings are considerably easier. However, the limitation or possibility of 2-D calculations and the necessity of 3-D calculation have only been examined analytically using very simplified structures [3].This paper describes the modeling of magnetic recording heads using 2-D and 3-D finite element method for various heads. Linear and nonlinear calculations of Metal-In-Gap and thin-film heads were carried out using 3-D T -0 141 and 2-D A-$ magnetostatic solvers. For 3-D meshing, an automatic mesh-generating pre-processor [5] was used. It was found that flux concentration as well as core thickness have to be carefully considered when trying to solve in two dimensions. It is confirmed that nonlinear 2-D calculations of MIG heads are acceptable. On the other hand, three-dimensional analysis is strongly recommended for thin-film heads. 11. ANALYSIS of MIG and THIN-FILM HEADS Figs. 1 (a) and (b) show the gap regions of a single-sided MIG, which has a metal film only on the trailing side, and a thin-film head, respectively. For the MIG head: gap length G,=0.5, throat height Gd=5 and half of the track width T,,/2=7.5 p. For the thin-film h a & G$.3, Gd=l.O and T,,/2=3.25pm.Note here that their track width is more than twenty times Manuscript received November 1. 1993. their gap length. Therefore, 2-D calculations may be applied [3] to these heads. We have examined the field distribution of these heads using 2-D and 3-D [4] calculations. Taking advantage of their symmetrical structures, the problems were halved and then divided into 3-D meshes by an automatic mesh-generating pre-processor [5]: for the MIG head, 335,566 tetrahedra and 57,523 nodes; for the thin-film head, 241,603 tetrahedra and 42,303 nodes. Figs. 2(a) and (b), respectively, show the gap region of the finite-element meshes of MIG and thin-film heads used for the calculations. For accuracy, several 3-D meshes were used for each model and no major differences were found. A. Linear CalculationsFor simplicity, linear calculations are sometimes used, especially for read-back processes. Fig.3 shows the calculated maximum recor...

Three-dimensional reconstruction of magnetic stray fields using reflection electron beam tomography

“…Here, we want to discuss equation (9). If the track width of a magnetic head is more than 20 times its gap length, then the field can be modelled in terms of a two-dimensional vector [10,11]. Even in narrower track thin-film heads, it has been found that B x records only in a small band at either edge of the head track [10].…”

“…Therefore, based on the relationship shown in equation ( 8), it is difficult to get a satisfactory initial B y (x, y, 0) and the corresponding procedure similar to equations ( 17) and (18) by which to get an accurate reconstruction result of B y on the head surface is also difficult. Here, attention must be paid to equation (11), which shows the relationships between D xm and B y (x, y, z). In the following part, we propose a method to separate the deflection effect of B y (x, y, z) from the mixed deflection effects of B y (x, y, z) and B z (x, y, z) (as shown by equation ( 11)) and then use this separated deflection effect of B y (x, y, z) to obtain a satisfactory initial B y (x, y, 0) on the head surface; and, furthermore, correct the initial B y (x, y, 0) along the y direction (across the head gap) to obtain an accurate reconstruction result of B y (x, y, 0) on the head surface.…”