Growth and magnetism of Fe on Cr(001): a spin-polarized scanning tunneling spectroscopy and magnetic force microscopy study

The growth and magnetic domain structure of Fe nanoislands and films on Cr(001) are investigated by spin-polarized scanning tunneling microscopy and magnetic force microscopy (MFM). Topographic images of films grown at different substrate temperatures reveal that the highest film quality is obtained by evaporation at room temperature and subsequent annealing at 500 K for 4 min. Spin-resolved studies of the magnetic structure of submonolayer Fe films (coverage 0.2 ML) show the expected antiferromagnetic Fe–Cr coupling, i.e. any Fe island is magnetized antiparallel with respect to the underlying Cr(001) terrace. As the Fe coverage exceeds 0.2 ML the magnetic contrast decreases and completely vanishes for 0.4 ML. Only for 3 ML does a weak magnetic contrast reappear, which is interpreted in terms of a small spatial variation of the 90° coupling between the Cr substrate and the Fe overlayer. MFM reveals that the number of visible domain walls decreases with increasing film thickness and completely vanishes at 12 ML. PACS 68.55.-a; 75.60.Ch; 68.37.Ef