Magnetic domain structure of micro-patterned PtMn/NiFe exchange bias bilayers

A bottom pinned exchange bias bilayer system consisting of 20 nm PtMn and 6 nm NiFe (produced using ion beam deposition (IBD) and physical vapour deposition (PVD, magnetron sputtering)) was laterally magnetic patterned by means of focused ion beam irradiation (FIB) on a micrometer scale. 25 keV ion irradiation with a fluence of
2×1014Ga+·cm−2 leads to a disordering of the as prepared chemically ordered PtMn-phase with only minor changes in sample topography. Thus the exchange bias field as well as the coercive field was reduced to a large extent on a local scale. The magnetic properties of FIB written 1µm wide stripes and their interaction with the non-irradiated spacing were analyzed by means of magneto-optic Kerr effect, magnetic force microscopy, and Kerr microscopy. The application of a magnetic field between -12
Oe and -80 Oe with respect to the exchange bias field direction leads to an antiparallel alignment of irradiated and non-irradiated stripes forming pronounced domain walls. A parallel alignment was found below -100 Oe and in the positive field region.