CEMS spectra of non-spherical nanoparticles in oxidized iron thin films

Room temperature CEMS spectra and field-cooled and zero field-cooled hysteresis loops have been measured on oxidized iron films of 100 nm thickness. The iron films were sputtered on a Si substrate, while the substrate temperature, Ts, was kept at 200 K and 300 K, and subsequently oxidized. The magnetization of the Ts = 200 K sample decreases ca. 40% with respect to the Ts = 300 K one, and a small exchange bias appears. The CEMS spectra show a preferential orientation of the magnetization of the films, which is more tilted toward a direction parallel to the film plane as Ts is decreased, which is attributed to a competition between shape anisotropies.