Core−Shell Cylindrical Magnetic Domains in Nickel Wires Prepared under Magnetic Fields

An experimental study of the magnetic domains of nickel wires prepared under magnetic fields was carried out by using magnetic force microscopy. Nickel wires with a diameter of approximately 250 nm had a single-domain structure, while unique core−shell cylindrical domain was found in 2-μm-diameter wires. It is suggested that this novel domain structure was formed because of the presence of a magnetic field during the formation of wires and strongly depended on the diameter of the wires.