Analysis of Written Transition Curvature in Perpendicular Magnetic Recording From Spin-Stand Testing

This paper presents a method of determining the transition curvature in magnetic recording, using only spin-stand measurements and a single read/write head. The method relies on finding an area of the disk in which the noise is in an as-deposited or bulk-erase state; the noise statistics can then be assumed to be independent of small changes in position across a track width. Trigger transitions are written on the disk and then the media noise is measured at many closely spaced positions across the track. From these multiple measurements, a 2-D picture of the noise referenced to the trigger can be created. This 2-D noise picture is distorted because of curvature of the trigger transitions. Assuming that the noise is truly stationary with respect to position, the underlying curvature of the trigger can thus be derived. On the basis of that derivation, any data pattern can be written and then read back and corrected for the known curvature on the trigger transitions. The paper compares the results obtained by this method with two different magnetic force microscope (MFM) observations. The new method shows, for example, that transitions written by a single-pole writer with a trailing shield writer have less transition curvature and transition noise than those written by a single-pole writer without any shield.