Accurate measurement of domain wall velocity in amorphous microwires, submicron wires, and nanowires.

A new method for measuring the domain wall velocity in a single, ultrathin ferromagnetic amorphous wire with the diameter down to 100 nm is presented. The method has been developed in order to increase the sensitivity in studying the domain wall propagation in bistable magnetic wires in a wide range of field amplitudes, with much larger values of the applied field as compared to those employed when studying the wall propagation in typical amorphous microwires. The large fields required to propagate the domain walls in ultrathin wires are able to nucleate new domain walls in the samples and, therefore, they can affect the accuracy of the entire measurement. The proposed experimental setup prevents such situations by using a number of complex pick-up coils, which allow the detection of the direction of the wall propagation along with the precise measurement of the domain wall velocity. The newly developed method is especially important now, when large effort is devoted to the development of domain wall logic devices based on ultrathin magnetic wires and nanowires.