Magnetic properties of Fe microstructures with focused ion beam-fabricated nano-constrictions

Studies of the magnetic properties of Fe microfabricated wires with a mechanically stable 40 to 120 nm-wide constriction produced with focused ion beam are reported. The 2 to 20 /spl mu/m-wide wires are fabricated by photolithography from 3 nm and 25 nm-thick epitaxial [110] bcc Fe films. This fabrication method appears to preserve the magnetic properties of the constriction. The structures are studied by MFM and by magneto-optic Kerr effect (MOKE) measurements. The ratio of the wire linewidth to its thickness determines the demagnetization factor and, therefore, influences the coercivity of the wire. Both a step in the width of the wire and a nano-constriction in the middle of the wire are found to be domain wall (DW) pinning centers.