Magnetic properties of Fe microstructures with focused ion beam-fabricatednano-constrictions

Studies of the magnetic properties of Fe microfabricated wires with a mecha nically stable 40 to 120 nm-wide constriction produced with focused ion bea m are reported. The 2 to 20 mum-wide, wires are fabricated by photolithogra phy from 3 nm and 25 nm-thick epitaxial (110) bcc Fe films. This fabricatio n method appears to preserve the magnetic properties of the constriction. T he structures are studied by MFM and by magneto-optic Kerr effect (MOKE) me asurements. The ratio of the wire linewidth to its thickness determines the demagnetization factor and, therefore, influences the coercivity of the wi re. Both a step in the width of the wire and a nano-constriction in the mid dle of the wire are found to be domain wall (DW) pinning centers.