Temperature dependence of magnetic properties in single crystal particles of cobalt

Abstract

Single crystal Co films (19–220 nm in thickness with their c-axis parallel to the surface normal) were epitaxially deposited onto Al 2O 3 ( 0 0 1 ¯ ) single-crystal substrates by electron beam evaporation, and from these films, Co particles with diameters of 0.5, 1, and 2.5 μm were fabricated by electron beam lithography and Ar ion beam etching. Magnetic domain structures of the films and the particles were observed by magnetic force microscopy (MFM) with temperature up to 200 °C. For the 220 nm thick sample's case, maze patterns in domain structure were clearly observed both in the film and the particles. MFM images taken at elevated temperatures do not show drastic change in the domain patterns. On the other hand, for the 56 nm thick sample's case, maze-type domain structure in the original film turns to concentric-type structure after patterning into particles, and furthermore, the domain structure exhibits vortex at 200 °C. Landau–Lifshitz–Gilbert (LLG) simulation for domain pattern visualization was also conducted, and the results show good agreement with experimental results of the 220 nm thick samples, though for the 56 nm sample's case the agreement is not so satisfactory.