Intermixing during epitaxial growth and Mössbauer spectroscopy with probe layers

Abstract

Mössbauer spectroscopy with 57 Fe ( 119 Sn) probe layers is a useful method to study the local magnetic structures at buried interfaces. However interface alloying, which always exists in the real samples, have to be taken into account for accurate interpretation of experimental data. We developed an algorithm, which describes the interface intermixing in the multilayers. Substituting deposited atoms by atoms of substrate and floating of deposited atoms in the upper layers during epitaxial growth leads to the formation of asymmetric chemical and magnetic interfaces. This asymmetry in the M 1 /M 2 superlattices can explain the difference between magnetic responses from M 1 on M 2 and M 2 on M 1 interfaces which were observed in experiments. Applying this intermixing model to the systems with probe layers located at different distances from the interfaces gives the natural explanation of hyperfine fields distributions on probe atoms and helps us clarify some discrepancies reported in the literature. Key words interface asymmetry . interdiffusion . hyperfine fields in multilayersInterface alloying is a common phenomenon, which always takes place to some degree during epitaxial growth of metallic multilayers. Atomic scale intermixing is one of the main types of interface roughness, and, therefore, it has to be taken into account for accurate interpretation of experiments. Mössbauer spectroscopy can be used to study the local magnetic interface structure in the superlattices with probe 57 Fe (or 119 Sn) layers. Insertion of such layers at set distances from the interface makes it possible to obtain the distribution of magnetic hyperfine fields (hff) in these particular layers [1]. The existence of probe atoms with various magnetic moments and with different local environments near the interface leads to the appearance of satellite lines in the Mössbauer spectra. However, interpretating these data happens to be a complicated and ambiguous task. If interdiffusion was present during the sample preparation process, the probe atoms are distributed in