Modeling of MIG heads using the boundary element method

Mini-composite metal-in-gap (MIG) heads for rigid disks are modeled using the boundary-element method (BEM) and compared with a standard ferrite ring head. It is shown that the head field gradient at the writing edge of an MIG head can be approximated by a Karlqvist head at high write currents, whereas a saturated ferrite head cannot. It is shown that MIG heads with films having saturation magnetizations of 10 kG and 15 kG can write media with maximum coercivities of 1240 and 1800 Oe, respectively. A small increase of an effective gap length can be used to account for the saturation of the C side of the core. Following the Williams-Comstock approach (1971), it is possible to use BEM calculations of head field distribution to obtain written transition length parameters. The transition length parameter of a ferrite head goes through a sharp minimum vs. magnetomotive force, whereas the transition length parameter written by an MIG remains essentially correct