Temperature dependence of magnetic domain structures of Co particles fabricated by electron beam lithography

Submicron-sized Co particles were fabricated by patterning single crystal Co thin films, and their magnetic domain structures were observed by magnetic force microscopy (MFM) with temperature up to 200 °C. The Co films (220 nm in thickness) were epitaxially deposited onto Al₂O₃ [001] single-crystal substrates by electron beam evaporation, and from these films (with their c-axis parallel to the surface normal) circular dots with diameters of 0.5, 1, and 2.5 μm were patterned by electron beam lithography and Ar ion beam etching. Maze patterns in domain structure were clearly observed in all types of dots. MFM images taken at elevated temperatures did not show prominent change in the domain pattern, which implies stability of Co magnetization up to this temperature. Landau-Lifshitz-Gilbert (LLG) simulation results showed good agreement with these experimental data, and also predicted that a vortex structure will be obtained with thinner (50 nm) dots at 200 °C.