Write Performance of Recording Heads with a High-Bs Pole for High-Hc Media

A magnetic recording head with a Co-Ni-Fe/Ni-Fe composite write pole was designed. The saturation induction Bs of Co-Ni-Fe is 2 T. In a computer simulation of a 3D static magnetic field, a recording head with Co-Ni-Fe films on both sides of a write gap generated a longitudinal write field of 9.9 kOe at a magnetic spacing of 40 nm from the write gap. The write characteristics of the recording head with the dual high-Bs structure designed above was tested for media with high coercivities of 4.5 to 7 kOe. The overwrite performance is over 30 dB for a medium with high coercivity of 7 kOe. Straight patterns of magnetic transitions written on the medium with a coercivity of 7 kOe were observed by using a magnetic force microscope (MFM). On the other hand, bends were found in the track-edges of magnetic transitions written on a medium with a coercivity of 4.5 kOe. This indicates that the recording head generated too large a write field for the medium with a coercivity of 4.5 kOe.