Magnetoresistance in magnetic nanoconstrictions: The role of structural defects.

The resistance of a ferromagnetic cylindrical Ni nano-constriction has been measured as a function of the external magnetic field. Typical profiles of the resistance versus external field are observed with irreversible jumps separated by stable plateaus, showing systematic slow relaxation effects. An interpretation in terms of magnetomechanical strain at the level of the constriction is proposed. This scenario allows the slow relaxation behaviour to be understood in terms of displacement of dislocations or similar metastable structural defects. [ABSTRACT FROM AUTHOR]