In the majority of cases nanostructures prepared by focused electron beam induced deposition (FEBID) employing an organometallic precursor contain predominantly carbon-based ligand dissociation products. This is unfortunate with regard to using this
high-resolution direct-write approach for the preparation of nanostructures for various fields, such as mesoscopic physics, micromagnetism, electronic correlations, spin-dependent transport and numerous applications. Here we present an in-situ cleaning approach to obtain pure Co-FEBID nanostructures. The purification procedure lies in the exposure of heated samples to a H$_2$ atmosphere in conjunction with the irradiation by low-energy electrons. The key finding is that the combination of annealing at $300^circ$C, H$_2$ exposure and electron irradiation leads to compact, carbon- and oxygen free Co layers down to a thickness of about 20,nm starting from as-deposited Co-FEBID structures. In addition to this, in temperature-dependent electrical resistance measurements on post-processed samples we find a typical metallic behavior. In low-temperature magneto-resistance and Hall effect measurements we observe ferromagnetic behavior.
Controlling magnetic properties on the nm-scale is essential for basic research in micro-magnetism and spin-dependent transport, as well as for various applications such as magnetic recording, imaging and sensing. This has been accomplished to a very
high degree by means of layered heterostructures in the vertical dimension. Here we present a complementary approach that allows for a controlled tuning of the magnetic properties of Co/Pt heterostructures on the lateral mesoscale. By means of in-situ post-processing of Pt- and Co-based nano-stripes prepared by focused electron beam induced deposition (FEBID) we are able to locally tune their coercive field and remanent magnetization. Whereas single Co-FEBID nano-stripes show no hysteresis, we find hard-magnetic behavior for post-processed Co/Pt nano-stripes with coercive fields up to 850 Oe. We attribute the observed effects to the locally controlled formation of the CoPt L1$_{0}$ phase, whose presence has been revealed by transmission electron microscopy.
