Magnetization reversal of exchange bias double layers magnetically patterned by ion irradiation

He+ ion irradiation is an excellent tool to modify the magnitude and direction of the exchange bias field on the sub-micrometer scale without affecting the sample topography. This effect has been utilized to magnetically pattern NiFe/FeMn exchange bias double layers using resist masks patterned by electron beam lithography. Ion irradiation through the masks leads to a local modification of the magnetization reversal behavior and allows to study the magnetization reversal as a function of the exchange bias field strength and the pattern dimensions on a single sample. Results are presented on the macroscopic and microscopic magnetization reversal using the magneto-optic Kerr effect and Lorentz microscopy.