LOCAL MAGNETISM OF FE IN FEIR(100) SUPERLATTICES STUDIED BY FE-57 MOSSBAUER SPECTROMETRY

The magnetic properties of Fe grown in FeIr(100) superlattices are inv estigated by Fe-57 Mossbauer spectrometry. Series of superlattices wit h 3 to 8 Fe-57 and/or Fe-56 atomic planes and It thicknesses from 2 to 30 Angstrom were prepared by molecular beam epitaxy. For the series w ith 4 Fe atomic planes with body-centered tetragonal (bet) structure, the occurrence of a sizeable magnetic moment in the two central Fe lay ers above a critical volume threshold is evidenced, whilst the Fe in c ontact with Ir keep weakly magnetic. For series with more than 4 Fe pl anes, the transition from the bet to the bcc structure results in new magnetic sites. The arrangement along the growth direction is detailed showing a magnetic dissymmetry between the Ir/Fe and Fe/Ir interfaces . Moreover, magnetic relaxation effects and spin wave softening are ob served, likely due to small magnetic correlations from plane to plane.