Arrays of Metal Nanostructures Produced by Focussed Ion Beam

We present a study of the magnetic properties of arrays of nanostructures produced in a focussed ion beam-scanning electron microscope dual beam system. The single magnetic units have been isolated either by direct removal of parts of the metallic film or by local modification of the film magnetic properties. The final quality of the shape and the residual damage strictly depend on beam parameters (spot size and pixel dwell time) and on the swelling properties of the patterned materials. On square Fe(001) elements with a well-defined intrinsic (magnetocristalline) and shape- and size-induced (shape plus configurational) anisotropy we show that the overall magnetic anisotropy is not a mere superposition of the individual contributions. We also demonstrate that with ion irradiation doses below the milling threshold L10 FePt films with perpendicular magnetic anisotropy undergo a transition from the magnetically hard L10 phase to the magnetically soft A1 phase leading to an out-of-plane to in-plane spin reorientation. The magnetic properties of the planar arrays obtained by local modification of the film are compared to arrays of sculpted structures of the same material.