Layer magnetization canting in 57Fe/FeSi multilayer observed by synchrotron Mossbauer reflectometry

Synchrotron Mossbauer reflectometry and GEMS results on a [Fe-57(2.55 nm)/FeSi (1.57 nm)](10) multilayer (ML) on a Zerodur substrate are reported. CEMS spectra are satisfactorily fitted by alpha-Fe and an interface layer of random alpha-(Fe, Si) alloy of 20% of the 57Fe layer thickness on both sides of the individual Fe layers. Kerr loops show a fully compensated AF magnetic layer structure. Prompt X-ray reflectivity curves show the structural ML Bragg peak and Kiessig oscillations corresponding to a bilayer period and total film thickness of 4.12 and 41.2 nm, respectively. Grazing incidence nuclear resonant Theta-2 Theta scans and time spectra (E = 14.413 keV, lambda = 0.0860 nm) were recorded in different external magnetic fields (0 < B-ext < 0.95 T) perpendicular to the scattering plane. The lime integral delayed nuclear Theta-2 Theta scans reveal the magnetic ML period doubling. With increasing transversal external magnetic field, the antiferromagnetic ML Bragg peak disappears due to Fe layer magnetization canting, the extent of which is calculated from the fit of the time spectra and the Theta-2 Theta scans using an optical approach. In a weak external field the Fe layer magnetization directions are neither parallel with nor perpendicular to the external field. We suggest that the interlayer coupling in [Fe/FeSi](10) varies with the distance from the substrate and the ML consists of two magnetically distinct regions, being of ferromagnetic character near substrate and antiferromagnetic closer to the surface.