Effect of pole tip alignment on magnetic fringing fields from recording heads

The effect of using pole tips of equal width in thin-film recording heads has been studied by examining a head having the track edges of its leading and trailing pole tips virtually aligned on one side and misaligned by 1.5 μm on the other. Magnetic fields produced by this head, as well as by a head whose edges were aligned by ion milling, have been measured. Using a magneto-optic photometer system with spatial resolution of less than 0.5 μm, the response of a thin-film medium spaced 0.25 μm from each head was dynamically monitored at a frequency of 1 MHz as the head was scanned beneath it. Results demonstrate that fringing fields emanate to a larger spatial extent in both dimensions from misaligned edges. These results are correlated with magneto-optic measurements of the dynamic response of the magnetization made directly at the pole tips of the two recording heads. Both a wider written track and broader transitions of magnetization are to be expected in a magnetic storage medium subjected to the fields in the vicinity of misaligned edges. This indicates that to achieve high track densities and to avoid interference from signals recorded on adjacent tracks as well as to minimize distortion during the read process due to a contorted field profile at misaligned edges, it is desirable to use heads with equal top and bottom pole widths.