The irreversible magnetization process in microstructured permalloy ellipses

Microstructured permalloy ellipses have been fabricated using electron-beam lithography through a lift-off process. The investigations were focused on the magnetization configurations and switching processes adopting magnetic force microscopy (MFM) and magnetoresistance (MR) measurements. An original five-vortex domain configuration of ellipse can be controlled and manipulated to become a four-vortex domain configuration by tuning the external magnetic field applied along the short-axis direction. In addition, an asymmetrical reversal process can be demonstrated on an ellipse having two- or three-vortex domain configuration, in which the switching fields are 36 Oe and 24 Oe, respectively.