High-speed creep effects in magnetic films

Creep measurements were made on single domain walls in thin magnetic films using high-speed pulses with variable rise and fall times (0.4 ns to s) and durations (<1 ns to 3 μs). Combinations of these pulses and dc fields were applied along the hard axis while simultaneously easy-axis dc fields were applied. The two basic measurements that were made were onset of creep and the distance the wall crept per pulse as a function of applied fields. Definite rise-time effects were found, the exact behavior depending on the domain wall structure. For Bloch walls, gyromagnetic effects of the total wall (similar to wall streaming) are present for rise times ns, whereas for longer rise times the Bloch to Néel wall transition appears to be responsible. For films thinner than 900 Å the existence of a cross-tie structure was found to be necessary for creep. For this wall structure the exact mechanism which causes creep enhancement for rise times <100 ns is unknown.