Magnetic properties of granular CoCrPt:SiO2 thin films deposited on GaSb nanocones

We report on the effect of microstructure and geometry on the magnetic properties of granular CoCrPt:SiO2 films with weakly interacting magnetic grains deposited on pre-structured GaSb nanocone templates fabricated by ion erosion technique. By tuning the irradiation conditions, nanocone patterns of different cone size were prepared (from 28 to 120 nm in diameter and 32 to 330 nm high, respectively). The influence of the intergranular exchange coupling was also investigated by varying the SiO2 content from 8 to 12 at.%. Deposition of CoCrPt:SiO2 on samples with small nanocones leads to a close magnetic grain packing, which results in the formation of extended magnetic domains larger than the average distance between the GaSb cones. In contrast, on larger nanocones, the magnetic coating grows on the side-walls with large separation between neighbouring cones leading to magnetic single-domain regions, which are correlated to the underlying structure. Magnetometry indicates that both remanence and coercivity decrease with increasing cone size and/or SiO2 content due to the combined effect of the angular distribution of the magnetic easy axis of the grains and the intergranular exchange coupling strength.