Observation of vertical Bloch lines using in-plane excitation fields

To study the motion of vertical Bloch lines (VBL) in stripe domain walls in ferrimagnetic garnet films the experimental technique of using pulse in-plane fields has been applied. In addition the dynamics of VBLs, single and in a pair, have been examined in numerical simulations based on J. Slonczewski´s equations of wall motion (1982). In contrast to the commonly used domain-wall rocking method, wall parts having no VBLs affected by the excitation field are used, therefore giving a better detectability of VBLs. For detection purposes a sinusoidal AC in-plane field has been applied. For measuring dynamic properties of VBLs, single pulses of in-plane field with amplitudes up to 12 Oe and pulse widths varying from 200 ns to 2 mu s have been used. The velocity of VBLs, their mobility and their coercivity has been measured. The VBL velocity saturates at about 55 m/s. The measurements include overshoot. Simulations show large overshoots caused by the reduction of wall bending after pulse termination. High-speed photography during in-plane field pulsing reveals that the reduction in wall bending in real material is small.