Experimental determination of anisotropy and demagnetizing factors of single Co nanowires by magnetoresistance measurements

We have investigated the low-temperature magnetoresistance (MR) behavior of Co nanowires with varying widths between 40 nm and 5.2 mu m prepared by high-resolution electron-beam lithography. The wires have a thickness of 20 nm and are protected from oxidation by a 10 nm carbon cap layer. The magnetoresistance-for magnetic fields applied transversal or perpendicular to the wire-is negative and can be attributed to anisotropic magnetoresistance. The MR curves exhibit a strong dependence on the wire width from which the shape anisotropy and the demagnetizing factors can be deduced. The experimental results are in perfect agreement with the theoretical values for the demagnetization tensor of the general ellipsoid. During the magnetization rotation process a minor contribution from domain-wall nucleation and annihilation occurs. (c) 2005 American.Institute Of Physics.