Magnetoresistance behavior of single castellated Ni80Fe20 nanowires

We have studied in a systematic way the magnetization reversal processes of single castellated Ni80Fe20 nanowires fabricated by advanced electron beam lithography. The structures consist of two 5 μm wide Ni80Fe20 support wires bridged with a castellated nanowire of width in the range from 80 to 150 nm. We have used the anisotropic magnetoresistance (AMR) effect as a probe of the spin orientations and hence magnetization reversal processes in these complex magnetic structures. When the applied fields are along the horizontal legs of the castellated nanowire, we observe a unique MR response due to the creation of magnetic local easy and hard axes resulting in a number of discontinuous jumps in the magnetoresistance. The magnetoresistance behavior is strongly influenced by spin states at corners of the nanowire for field applied parallel or perpendicular to horizontal legs. These results are in agreement with simple micromagnetic simulations.