Magnetic behavior of metastable Fe films grown on Ir(111)

We investigated the growth of ultra-thin Fe films on Ir(111) by means of <i>in-situ</i> low energy electron diffraction and spin-resolved photoemission techniques. We observe a (1x1) diffraction pattern, characteristic of the <i>fcc</i> substrate, below 4 monolayers (ML). Then, a complex superstructure starts to develop, compatible with the formation of <i>bcc</i>-like Fe domains aligned with the substrate according to the Kourdjumov-Sachs orientation relationships. The analysis of the diffraction patterns reveals a progressive evolution towards a fully relaxed <i>bcc</i> lattice, characteristic of bulk Fe. Both photoemission (filled states) and inverse photoemission (empty states) results show characteristic features related to the contribution of the Fe layer, evolving towards those observed on the Fe (110) <i>bcc</i> surface. Spin resolution allows to detect a spectral polarization above 4 ML corresponding to the formation of bcc Fe, which gradually increases indicating the formation of an in-plane magnetized ferromagnetic layer in thick films. No in-plane net magnetization is detected in thinner films, independent of the sample temperature down to 30 K. Following recent investigations on the Fe/Ir(111) system with microscopy techniques, we link this observation to the stabilization of a non collinear spin structure yielding an overall nil magnetization.