Investigation of very low-frequency noise in ferromagnetic nickel nanowires

In this paper we report very low-frequency (0.1 mHz-1.0 Hz) resistance fluctuation (noise) in Nickel nanowires of diameter 20 nm in the temperature range 77 K-300 K. The wires are one-dimensional magnetic systems since the diameter is less than the domain wall width. We found a clear signature of deviation of the spectral power from 1/f noise at low frequencies showing excess fluctuations with very slow dynamics. The magnitude of resistance fluctuations increases by an order of magnitude when the diameter of the wires is reduced below the domain wall width of nickel. The excess resistance fluctuation has been linked to thermally activated magnetization reversal and the associated domain wall motion.