Observations of domain-wall dynamics in cylindrical magnetic films

Direct observations using the Bitter technique of domain-wall dynamics in 1000-Å-thick Ni-Fe-Co cylindrical films are reported. It is found that the bit which forms under the word strap is defined by labyrinth domains if unipolar write cycles are used. The Waaben write cycle, in which a unipolar cycle is followed by a reverse easy direction pulse φ2, tends to form bits defined by simple circumferential ring walls. The results of unipolar pulse mobility measurements are in good agreement with previous data on flat films. However, the results of bipolar pulse mobility measurements show that the wall translation distance is anomalously low when bipolar pulses are applied. By adjusting the amplitude and length of φ2in the Waaben write cycle, it is shown that wall motion can be eliminated for hxabove and below hw, the wall motion coercive force. The effectiveness of φ2for is consistent with those models for creep in which local variations in hwplay a major role.