Imaging microspectroscopy of Ni/Fe/Co/Cu(001) using a photoemission microscope

The magnetic phases of 0-6 atomic monolayers (ML) Ni/0-14 ML Fe/6 ML Co/Cu(001) trilayer crossed double wedges are studied by the combination of photoelectron emission microscopy and X-ray magnetic circular dichroism spectroscopy at the Fe L2,3 edges. This microspectroscopic technique allows the extraction of local quantitative magnetic information. The presence of three magnetically different thickness regions of Fe with effective spin moments per atom of 2.5 µB (below ~3.5 ML), 0.7 µB (~3.5-11 ML), and 2.0 µB (above ~ 11 ML) is confirmed. At 7-9 ML thickness, the value of 0.7 µB is consistent with a ferromagnetic Fe surface layer on top of non-ferromagnetic layers. The ratio of orbital to effective spin moment varies between 0.05 for very thin Fe films and 0.15 for thicker films, if correction of saturation effects is taken into account. Images of the magnetic circular dichroism asymmetry at the Ni and Co L3 edges show that at 5.5 ML Fe thickness the Ni and Co magnetizations have opposite orientations, pointing towards antiferromagnetic coupling across the Fe layer.