Spin-polarised neutron reflection studies of epitaxial films

Abstract

The application of polarised neutron reflection (PNR) to investigations of the static magnetic properties of ultrathin epitaxial films is discussed. PNR yields the absolute value of the magnetic moment per atom of sandwiched monolayer thickness films with high accuracy, while in contrast with SQUID magnetometry for example, no magnetic signal requiring correction arises due to the substrate. PNR also provides valuable information relating to the interface quality. The roughness amplitude and correlation length can be estimated from the specular reflectivity and the angular width of the diffusely reflected beam respectively. We discusse the observed dependence of the magnetisation upon the transition metal layer thickness in the 1–10 ML range for Ag/Fe/Ag(001), Ag/Co/Ag(001), Cu/Co/Cu(001) and Ag/Cr/Ag(001) sandwich structures as an illustration of PNR as a magnetometric technique. The sensitivity of the wavevector-dependent reflectivity to the layer dependent magnetisation is illustrated by our recent investigations of sputtered Fe/Cr/Fe layers in the antiparallel coupling regime and of a ‘thick’ bcc Co/GaAs(001) film.