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Abstract

The proposal of logic- and memory devices based on magnetic domain-wall motion in nanostructures created a great demand on the understanding of the dynamics of domain walls. We describe the controlled creation and annihilation of domain walls by Oersted-field pulses as well as their internal dynamics during motion. Electric measurements of the magnetoresistance are utilized to identify permanent- or temporal creation and continuous motion of domain walls initiated by nanosecond short field pulses in external magnetic fields. The injection of domain walls into nanowires with control of their magnetic pattern (transverse or vortex), their type (head-to-head or tail-to-tail magnetization orientation) and their sense of magnetization rotation (clockwise or counter clockwise chirality) is reliably achieved. Influencing the creation process of consecutively created domain walls to obtain multiple walls inside one wire or to mutually annihilate the walls is found to be possible by changes of magnetic field parameters. The time structure of the creation process is analysed by time-resolved transmission X-ray microscopy. After complete formation wall transformations are observed above a critical driving field known as the Walker breakdown. Internal excitations of vortex domain walls are also found in low field motion. A strong interplay between internal dynamics and the macroscopic motion is identified.