Ultra-high-vacuum magnetic force microscopy of the domain structure of ultra-thin Co films

Two scan modes were developed for an Omicron atomic force microscope/scanning tunneling microscope (AFM/STM) operating in ultra-high vacuum (UHV). These modes allow scanning at a constant tip-sample distance in order to measure forces or force gradients. Samples and tip probes were prepared and used in the same UHV system. Co films were deposited on Si substrates by electron beam evaporation. The thickness of these films was 2-120 monolayers (ML). Si tips, coated with 20 ML Fe, were used as probes. The Co films showed a magnetic structure with in-plane magnetization. Cross-tie domain walls were also observed. Furthermore, the Co him was sensitive to forces exerted by the tip on the sample in contact AFM mode.