Writer Field Gradient Measurement on Spinstand

The gradient of magnetic head field is very critical in the writing process and it is one of the key factors to determine the achievable linear density of magnetic recording system. This work proposed a new method to measure the writer field gradient on Spinstand. The even harmonic ripple effect [4] is used to produce the modulated magnetostatic field at the writing transitions generated from the old data pattern at leading edge side of the writer. The newly written single tone signals have the modulated transition shift. Through the duty cycle measurement of the single tone signals, the delta transition shift can be measured. With the calculated magnetostatic field based on the media magnetic properties and the measured size of writer footprint, the writer field gradient equals the ratio of delta magnetostatic field over delta transition shift.