Structural and magnetic phase transitions of Fe on stepped Cu(111)

The magnetism and its correlation with morphology and structure of ultrathin Fe/Cu(111) films have been studied. At room temperature, the films grow in a quasi-one-dimensional form (stripes) in the submonolayer range. Between 1.4 and 1.8 ML the stripes percolate and become two-dimensional films. The remanent magnetization of the percolated films was observed to be significantly more stable with respect to time than that of the stripes. At low thickness (2.3 ML) the films adopt the fcc structure from the substrate and later transform to bcc(110) structure with Kurdjumov-Sachs orientation. Experimental evidence suggests that the fcc films have a low-spin ferromagnetic or ferrimagnetic phase, and a perpendicular easy magnetization axis. The magnetization switches to an in-plane high-spin phase after the fcc to bcc structural transformation has been accomplished.