Magnetic domain instability in MR heads due to overlaid structure of permanent magnet film

A permanent magnet (PM) film easily forms an overlap structure on a magnetoresistive (MR) film due to the overspray of sputtered material in the deposition process. This overlap structure of a PM film affects the stability of the magnetic domain structure in a MR element. The calculation model in this study takes account of the overlaid structure of a PM film without an interlayer exchange coupling. A large hysteresis was observed in the transfer curve due to a counter bias against longitudinal bias field in the case of 0.3 to 0.5 μm overlaid PM width. Also, the micro-track profile showed a double peak profile caused by the multidomain state in the MR element. However, in the case of 0 to 0.2 μm overlaid PM width, hysteresis of the transfer curve was reduced and a single peak micro-track profile was obtained. Consequently, the overlap PM width should be controlled below 0.1 μm in order to achieve the readback stability of the MR element