Dimensional crossover in the magnetism of MBE-grown Fe(110)/Ag(111) multilayers

Abstract
Fe(110)/Ag(111) heterostructures, composed of fixed 3 monolayer (ML) Fe bilayers and variable‐thickness Ag bilayers, were grown by molecular‐beam epitaxy and investigated by transmission Mössbauer spectroscopy in the temperature range from 4.2 to 300 K. We found that as the Ag layer is thick enough (≳17 ML) to magnetically isolate the neighboring Fe layers, a quasilinear temperature dependence of the Mössbauer hyperfine field results due to the two‐dimensional spin‐wave excitations. As the Ag layer is reduced to 4 ML, a dimensional crossover in the spin‐wave excitations is induced by the magnetic interaction between neighboring Fe layers which makes the magnetic temperature dependence change from a two‐dimensional T‐linear relation to a three‐dimensional T3/2 dependence.