Hard Axis Direction Research Articles

Wall streaming, creeping, and a new parade motion in Ni-Fe films excited by hard-axis pulses

The basic mechanism of Bloch wall motion associated with very-fast-rise-time hard-axis pulses appears to be the same for wall streaming or worm motion, creep, and a new uniform motion. Creep under these conditions as distinguished from creep excited by relatively low-frequency sinusoidal excitation must involve important gyromagnetic effects and exhibits the same threshold behavior as wall streaming and the new uniform motion. Creep may be associated with either an applied easy-axis bias or with an equivalent stray-field bias. The uniform motion is more easily produced in thicker films (1500 Å) with very small or no bias and consists of a "parade" of tip domains, first nucleated at the film edge and then moving in the hard-axis direction until annihilated at the edge. The threshold field for wall motion in all of these processes depends on the rate of change of the pulse field, increasing with increasing rise time. The threshold field decreases with easy-axis bias and is related to a characteristic coercive force. The movement per pulse increases with increasing magnitude of drive field to a maximum and then decreases. Several mechanisms are suggested for this behavior.