This paper discusses the relationship between the effective write track widths of thin-film heads and the coercivities of thin-film disks. The off-track performances of the output amplitudes and media-noises were investigated by using Co-Cr-Ta sputtered thin-film disks with different coercivities. The effective write track width becomes larger with an increase in the disk coercivity if the gradient of the head write field is large. If the gradient of the head write field is small, the wavelength of the zigzag wall becomes short and its amplitude becomes large in the track width direction of the transition regions. At the track edges of the transition regions, the track width direction component of magnetization increases because of the bitpattern bridging between the neighbor transitions.
