Uniform magnetization rotation in single ferromagnetic nanowires

Using electrochemical deposition, $6\mu \mathrm{m}$ long Ni nanowires, with typical diameters of the order of 80 nm, are grown in ion-track etched membranes. Electrical contacts are established during the growth, allowing measurements of single wires. The full magnetoresistive hysteresis loop is studied as a function of the angle between the applied field and the wire direction. For each field sweep, a discontinuity is observed. It corresponds to the irreversible switching of the magnetization. A model of uniform reversal of the magnetization accounts for the reversible part of these magnetoresistive loops using the conventional ${\cos }^2\omega$ dependence of the resistance with the angle $\omega$ defined between magnetization and electric current. The angular dependence of the switching field is discussed.