Evolution of the magnetic hyperfine field profiles in an ion‐irradiated Fe60Al40 film measured by nuclear resonant reflectivity

• Published in: Journal of synchrotron radiation 2021-09, Vol.28 (5), p.1535-1543
• Main Authors: Andreeva, Marina, Smekhova, Alevtina, Baulin, Roman, Repchenko, Yurii, Bali, Rantej, Schmitz-Antoniak, Carolin, Wende, Heiko, Sergueev, Ilya, Schlage, Kai, Wille, Hans-Christian
• Format: Article
• Language: English
• Subjects: Angle of reflection; Critical angle; Evolution; Ferromagnetic materials; Ferrous alloys; Fluence; hyperfine interactions; Hyperfine structure; ion irradiation; Irradiation; magnetic depth profiles; magnetic patterning; Mössbauer spectroscopy; nuclear resonant scattering; Reflectance; Selectivity; Silicon dioxide; Standing waves; Substrates; Synchrotron radiation; Synchrotrons; X‐ray reflectivity
• ISSN: 1600-5775; 0909-0495; 1600-5775
• DOI: 10.1107/S1600577521007694

Nuclear resonant reflectivity (NRR) from an Fe60Al40 film was measured using synchrotron radiation at several grazing angles near the critical angle of total external reflection. Using laterally resolved measurements after irradiation with 20 keV Ne+ ions of gradually varying fluence of 0–3.0 × 1014 ions cm−2, the progressive creation of the ferromagnetic A2 phase with increasing ion fluence was confirmed. The observed depth selectivity of the method has been explained by application of the standing wave approach. From the time spectra of the nuclear resonant scattering in several reflection directions the depth profiles for different hyperfine fields were extracted. The results show that the highest magnetic hyperfine fields (∼18–23 T) are initially created in the central part of the film and partially at the bottom interface with the SiO2 substrate. The evolution of the ferromagnetic onset, commencing at a fixed depth within the film and propagating towards the interfaces, has been directly observed. At higher fluence (3.0 × 1014 ions cm−2) the depth distribution of the ferromagnetic fractions became more homogeneous across the film depth, in accordance with previous results. Nuclear resonant reflectivity (NRR) was measured from an Fe60Al40 film irradiated by 20 keV Ne+ ions with gradually varying fluences of 0–3.0 × 1014 ions cm−2. The evolution of the ferromagnetic onset, starting from the central part of the film and propagating towards the interfaces, was revealed by the fit of the NRR time spectra.