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(a) Image captured by scanning a TMR read sensor over the writer pole tip and measuring the sensor signal. The trapezoidal writer pole tip and the trailing shield above it are visible similar to the schematic (b). The nominal width of the trailing edge of the pole tip is 125 nm. The imaging process is used to align the TMR read sensor on the writer pole tip.
Averaged time-domain data of measured write fields from the pole tips of two different writer designs expected to have different rise times at the same drive current. The data are fitted to an exponential function (smooth curves) that yields time constants of 243 and 96 ps for design 1 and design 2, respectively. The write driver waveform is also shown for comparison. Each curve is normalized to the root-mean-squared amplitude of the full time trace (not shown) for that design to better compare the shapes of the curves.
Real-time data for a head exhibiting a dynamic instability where pole tip reversal is sometimes inhibited by an intermediate transient state due to an antiferromagnetic coupling layer in the main pole. (a) A scope capture is broken up into segments equal to one period of the write driver clock (20 ns) and then overlaid (points). The median curve of the 650 segments is shown as a solid curve. (b) A selected portion of the same data as captured. A 50 MHz square wave (dashed curve) is overlaid to show the expected positions of the waveform transitions based on the median curve. The dynamic instability can be seen at the first and third falling edges.
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