Temperature dependence of the magnetization reversal process in patterned Ni nanowires

The magnetic behaviour of patterned Ni wires has been studied by magnetotransport measurements to analyse the mechanisms that govern the magnetization reversal in these ordered nanostructures as a function of temperature in the 150-350 K range. These results show reversal processes driven by a temperature-dependent combination of two different mechanisms: coherent rotation and a curling-like irreversible process. When the field is decreased from saturation the magnetization rotates reversibly until it reaches the nanowires' direction where it reverses its sign by an irreversible process at low fields. The amplitude in the magnetoresistance of this irreversible process is reduced as the temperature is increased, with a sharp step at room temperature. In fact, the analysis of the angular dependence reveals that it is compatible with an incoherent curling process up to 300 K in the whole angular range. For higher temperatures, a crossover towards coherent rotation is observed in the irreversible contribution for high angles between the applied field and the wire direction.