Influence of head fields and media properties on transitions of magnetization reversals on thin film disk

The authors describe a relationship between transition lengths and head fields for media of various coercivities. Signals with various transition lengths were written using a single-sided and a double-sided MIG head on three different thin film media having coercivities of 874, 1121, and 1270 Oe, respectively. The transition lengths were observed by the colloid SEM method. The head fields of the MIG heads were analyzed by the finite element method (FEM) with magnetic saturation taken into account. The following phenomena were discovered: (1) the secondary fields stray from the saturated ferrite region near the interface between the metal film and ferrite core of the MIG heads; and (2) the transition lengths are elongated due to the influence of the secondary field when the strength of the secondary field is greater than half of the medium coercivity. If the medium coercivity is twice as great as the secondary field strength, the transition length is closely related to the field gradient of the primary field in the recording zone.