In-situ measurement of reader gap length

We are presenting a technique to perform the reader-gap length in-situ measurement. It utilizes the presence of the first gap minimum on the third harmonic readback signal spectrum to calculate the electrical reader-gap length, and factor the electrical result to the physical reader-gap length. Compared with existing metrology-based methods, the measurement is non-destructive, dynamic, and insensitive against the skew angle change.