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/s canning 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 we re prepared and used in the same UHV system. Co films were deposited o n Si substrates by electron beam evaporation. The thickness of these f ilms was 2-120 monolayers (ML). Si tips, coated with 20 ML Fe, were us ed as probes. The Co films showed a magnetic structure with in-plane m agnetization. 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.