Domain wall resistance and magnetoresistance of narrow ferromagnetic wires

We report new experimental results for the transport properties of very nar row Ni wires. By suitable preparation with a magnetic field applied paralle l to the axis of a wire it is, possible to introduce domain walls, or to sw eep all walls out of a sample. We find that domain walls make a contributio n to the resistance which is negative. When a field is applied perpendicula r to the axis of a wire, the resistance exhibits abrupt steps and hysteresi s which suggest that rather modest perpendicular fields are able to nucleat e domain walls, and enable us to measure the resistance of a single domain wall. (C) 2001 Elsevier Science B.V. All rights reserved.