Tadashi Yasunaga

Magnetic duplication for precise servo writing on magnetic disks

A servo pattern of a 20 Gbit/in/sup 2/ level was directly duplicated on hard disks by using a magnetic duplication method, and the accuracy of the signal and the following performance on the duplicated servo pattern were evaluated. The phase servo pattern was composed of straight lines and was lithographically formed on a mastering disk. The period accuracy of the readback signal was very high. The repeatable position error for adjacent tracks in a prototype drive was measured, and the difference between two adjacent RPE trajectories was sufficiently small. The magnetic duplication method showed the possibility of precise servo-track writing for high-density hard disk drives.

Magnetic Recording Performance of “Bit Printing Method” on PMR Media and Its Extendibility to the Higher Areal Density

Servo pattern printing which supports bulk magnetic transfer of the servo pattern is expected to be the ultimate solution for perpendicular magnetic recording (PMR) media servo track writing method. There are two printing methods, ldquoEdge Printing (EP)rdquo and ldquoBit printing (BP)rdquo for PMR media. The reproduced waveform of EP method is not compatible with head writing. On the other hand, BP method is able to give the waveform like head write. We examined BP characteristic of the short bit length recording and its extendibility. The reproduced waveform of BP at 70 nm bit was equivalent to the head writing in its shape and amplitude. The spacing loss factor of BP was about 8 dB, and the signal-to-noise ratio of reproduced waveform had its peak at the point where Ha was close to Hc of recording media. It was easy to apply larger Ha by BP method than EP method, and magnetic printing signal had no write stitching problem that was seen in head writing especially at outer diameter area. There was no significant concern to increase Ha on BP, and BP was suitable for the future short bit length pattern.