Irreversible wall motion in inductive recording heads

The effect of signal-induced irreversible domain wall motion on the isolated transition response of recording heads is investigated. An experimental method is presented allowing differentiation between the effects caused by irreversible wall motion and reversible wall motion. The method, utilizing the injection of a small DC current into the head coil, can also be used to determine whether the irreversible motion in a thin-film head occurs in the first pole tip, the second pole tip, or the backgap. The transients observed result from signal-induced irreversible wall motion in the second pole tip. The largest isolated impulse variations occur after saturation of the yoke. In addition, it is found that Barkhausen transitions can occur at or near the top of the isolated impulse (even on its leading edge) as well as after the impulse has decayed, and not only on the trailing edge of the impulse as reported previously. Finally, the authors observe two Barkhausen-noise-free zones, the one at the leading edge being the largest