Low temperature electrical transport in ferromagnetic Ni nanowires

We report the electrical transport properties of arrays of nickel nanowires (diameters ranging from 55 to 13 nm) fabricated by electrodeposition into the cylindrical pores of anodic alumina membranes. X-ray and transmission electron microscope based characterization ensured single crystalline nature of the nanowires. We have measured the resistance of the nickel nanowires in the temperature range of 3-300 K with the specific aim of probing the effect of size reduction on the temperature dependence of resistivity. As the lateral dimension decreases, deviations from the bulk resistivity are observed. Our work reveals intrinsic differences in the transport mechanisms taking place in these wires when the diameter of the wires is brought down from bulk to nano regime. The resistance data has been analyzed using the Bloch-Wilson function and the Debye temperature (theta(R)) was calculated from the fits. The Debye temperature showed a systematic decrease with decrease in diameter, which we note is a trend in other fcc metals such as Ag and Cu. We observed an increase in the residual resistivity as the diameter decreases due to surface scattering. We further observe a strong suppression in the spin wave contribution to the resistivity of the magnetic nanowires as the diameter is decreased. We discuss the likely causes for these changes.