Single-pole-type head with multicharged surfaces for ultrahigh density recording

A multicharged surfaces single-pole-type (MCS-SPT) head whose pole tip is formed from two steps of a wide cross section and a narrow one is proposed in order to improve writability of the conventional SPT head. A field from the wide tip can modify a recording field of the narrow tip in terms of not only the field strength but also the gradient. The field strength of the MCS-SPT head combined with a soft backlayer (SBL) of a double-layered medium was calculated by using a surface charge method. The superimposed net field strength becomes high by increasing the wide tip width and can largely surpass the saturation flux density (BS) of the head material like an electromagnet. The allowable maximum field of the wide tip should be determined by a negative nucleation field (HN) of a medium. A time decay of medium magnetization can not be observed for a dc field less than HN but can be more for that than HN. It has been confirmed also by a finite element method that the 100 nm track-wide MCS-SPT head combined with SBL separated by 30 nm from the narrow tip whose BS was 19 kG can generate the recording field strength of 23 kOe.