Experimental study of track edge noise distribution in narrow track recording

Time domain measurements were conducted on a precision spin stand tester to obtain two dimensional mappings of track edge noise in longitudinal thin film media. Read back voltage waveforms were repeatedly captured by a real time digitizer, and media noise power was obtained by calculating the ensemble variance of the waveform. The same procedure was repeated for different track positions ranging from on-track to totally off-track, and a two dimensional mapping was obtained. A conventional untrimmed thin-film inductive head was used to record the data patterns. On readback, a magneto-resistive read head was used because of its relatively narrow cross-track sensitivity function. Away from transitions, edge noise is uncorrelated and is distributed only along the sides of the hard-bit cells whose magnetization is reversed with respect to the original DC-erase direction. Edge noise enhancement is found when two hard-bit cells are placed in close proximity