Electron-electron interaction in carbon-coated ferromagnetic nanowires

We have investigated the low temperature resistance behavior and the magnetoresistance of single-domain cobalt nanowires of various thicknesses ranging between 50.3em0exnm and 320.3em0exnm and wire widths ranging down to 320.3em0exnm. The nanowires are coated with insulating carbon on three sides to prevent oxidation. Magnetic force microscopy investigations show that nanowires with widths below 8000.3em0exnm are in a single-domain-like remanence state. The magnetoresistance is negative and is well explained by the anisotropic magnetoresistance (AMR). At low temperatures T<300.3em0exK a logarithmic resistance increase is observed with decreasing temperature, which is consistently explained as originating from enhanced electron-electron interactions in two dimensions. Quantum corrections due to weak electron localization are not observed which is in contrast to recent theoretical predictions for two-dimensional ferromagnetic systems. However, the results are consistent with our earlier results obtained for platinum-capped and unprotected cobalt nanowires. A reduction of the wire width below about 4000.3em0exnm yields a crossover behavior from two-dimensional to one-dimensional behavior with respect to the quantum corrections of the resistance.