Abstract
Magnetization processes in microfabricated NiFe wires were observed by using a Kerr microscope equipped with an oil-immersion lens (NA = 1.3) and an Hg lamp. NiFe wires 20 nm in thickness were prepared by using lift-off techniques. The width (W) of the wires was designed as 0.5, 1.0 and 2.0 μm and the length (L) as 50 μm. One end of the wire was connected to a square-shaped head with a side of 2 W, which was designed to act as a domain wall source. In each wire, necks of different widths were introduced as artificial pinning sites of a domain wall. Magnetization reversals in very narrow wires with 0.5 μm width were clearly observed. It was confirmed that domain wall penetration, pinning, depinning, and also the direction of wall motion can be controlled by using square-shaped head and necks with optimized width. The Kerr microscope image with the domain wall near the neck is almost consistent with the Kerr effect image obtained by micromagnetic calculation.
