A method for magnetization reversal measurements in submicron magnetic wires was developed by utilizing the giant magnetoresistance effect, which enables us to determine a domain wall position as ii function of time, and allows to evaluate the propagation velocity of the domain wall easily. It was found that the magnetization reversal in a wire occurs in association with the propagation of a single domain wall and that an artificial neck introduced into the wire :acts as a pinning site of the magnetic domain wall. Injection of the magnetic domain wall from one end of the wire is demonstrated. Results on electric resistance measurements down to 20 mK for ultranarrow Ni wires are also presented. An increase of resistance proportional to T (1 2) was observed in a temperature range from 10 K to 80 mK. The result is discussed in terms of the electron -electron on interaction and the weak localization effects. (C) 2001 Elsevier Science B.V. All rights reserved.