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A Low Fly Height and High Moment Wide Write Head for Disk Certification Test Disclosure Number: IPCOM000016096D
Original Publication Date: 2002-Oct-28
Included in the Prior Art Database: 2003-Jun-21

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This disclosure describes the use of a low flying height and high moment wide write head for the disk magnetic certification test. The problem being addressed is the need for detecting small defects, such as short circumferential narrow scratches, and writing on high coercivity disk at high density. The invented head is capable of achieving the objectives with low fly height and high moment write element, as well as high write track to read track width ratio. As recording density increases at a rate of more than 60% annually, higher coercivity disks are needed. This in turn requires better write ability of the head. Another challenge for the head is the detecting of small disk defects, which is critical for product quality control. The low fly height (10.5 nm at normal pressure, Fig. 1) and high moment of the invented head makes it able to write well on disks with coercivity as high as 5000 Oe, as can be seen from the overwrite (OW) vs. write current curve for three such heads (Fig. 2). The write track width of the head, 6.1 um, is much wider than the read track width, 0.42 um. The wide write track width ensures that the reader reads the signal with no off track concerns. The very narrow read track width makes the head very sensitive to narrow circumferential scratches. This can be seen more clearly with the help of Fig. 3. Assuming the magnetic film of the scratched portion has been totally removed, the read signal amplitude drop in percentage is SW/RW . Thus the narrower the read track width the higher the amplitude drop for a circumferential scratch with given width. Test results show that the invented head is able to detect defects as small as 0.16 um. 11.0