Patent ID: 8638518

Claim:
A servo writing system comprising: a magnetic tape erasure unit positioned along a tape path and configured to substantially demagnetize a magnetic tape medium, the erasure unit comprising: a first set of magnetic elements; and a second set of magnetic elements, the magnetic elements in the first and second sets positioned to define an alternating configuration, wherein the magnetic elements in the first and second sets of magnetic elements are configured to respectively produce magnetic fields of opposite polarity; a bias magnet configured to create a remnant magnetization of at least 20 percent on a full width of the substantially demagnetized magnetic tape medium, wherein the bias magnet is a last magnetic element along the tape path in the second set of magnetic elements and is mounted to a stage, the stage configured to adjust the distance between the bias magnet and the tape path; and a servo write head positioned along the tape path and configured to write servo tracks on the remnant magnetized magnetic tape medium.