Magnetic and structural properties of ultrathin Mn and Fe films on Ir(111)

Abstract

We have measured the structural and magnetic properties of ultrathin Mn and Fe films grown on Ir(111). For Mn films a (1×1) to (√3×√3) phase transition is observed by low energy electron diffraction (LEED) at 4 monolayers coverage. The average magnetic moment in the Mn films was measured by both Mn 3s photoemission and Mn L2,3 absorption. The average Mn moment was found to decrease for thicker films. This decrease in the moment continues smoothly through the (1×1) to (√3×√3) phase transition, showing that the change in magnetic moment is not due to the phase change. A simple model, which assumes an enhanced moment in a single layer, explains the decrease in the magnetic moment well. For Fe films, changes in the LEED patterns at 5 ML are consistent with a face-centered-tetragonal to body-centered-cubic (fct to bcc) phase transition. Ferromagnetic ordering in the Fe thin films is observed by x-ray magnetic circular dichroism (XMCD) for films thicker than 5 ML. The onset of ferromagnetic ordering at 5 ML is due to the fct to bcc phase transition. The Fe L2,3 XMCD intensity is saturated at 10 ML showing that the entire film is magnetized and that no magnetic dead layer is present.