Abstract: A method is disclosed for writing servo patterns for tracks on a rotating magnetic disk medium of a magnetic disk drive. In the method, track following is performed along a reference track, defined by previously written servo burst patterns, using a servo loop having a closed-loop response. A position error signal is generated for the reference track based on the track following. A correction signal is generated based on the track following using an observer of a one-dimensional state model that is equivalent to the two-dimensional state model of the servo loop. Servo patterns are written at a target radial location on the magnetic disk medium during track following of the reference track. The position error signal of the servo loop is adjusted based on the correction signal to reduce radial error propagation from the reference track to the servo burst patterns at the target radial location.

Abstract: A hard biased spin-dependent tunneling sensor and manufacturing method therefor is provided having a substrate with a first lead formed thereon. A hard magnet is formed over the first lead and a free layer is formed over the hard magnet. A tunneling barrier layer with a first pinned layer formed thereon is formed over the free layer. A nonmagnetic coupling layer with a second pinned layer formed thereon is formed over the first pinned layer. A pinning layer is formed over the second pinned layer and a second lead is formed over the pinning layer.