Pure nuclear Bragg reflection of a periodic 56Fe/57Fe multilayer

Grazing incidence nuclear multilayer diffraction of synchrotron radiation from a periodic stack of alternating 56Fe and 57Fe layers was observed. Resonant layer fraction, substrate size, flatness, and surface roughness limits were optimized by previous simulations. The isotopic multilayer (ML) sample of float glass/57Fe(2.25 nm)/[56Fe(2.25 nm)/57Fe(2.25 nm)]×15/Al(9.0 nm) nominal composition was prepared by molecular beam epitaxy at room temperature. Purity structure and lateral homogenity of the isotopic ML film was characterized by magnetometry, Auger electron, Rutherford backscattering, and conversion electron Mossbauer spectroscopies. The isotopic ML structure was investigated by neutron and synchrotron Mossbauer reflectometry. Surface roughness of about 1 nm of the flat substrate (curvature radius >57 m) was measured by scanning tunneling microscopy and profilometry. A pure nuclear Bragg peak appeared in synchrotron Mossbauer reflectometry at the angle expected from neutron reflectometry while no ele...