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Abstract. Carbon and nitrogen austenites, modeled by Fe 8 N and Fe 8 C superstructures are studied by full-potential LAPW method. Structure parameters, electronic and magnetic properties as well as hyperfine interaction parameters are obtained. Calculations prove that Fe-C austenite can be successfully modeled by ordered Fe 8 C superstructure. The results show that chemical Fe-C bond in Fe 8 C has higher covalent part than in Fe 8 N. Detailed analysis of electric field gradient formation for both systems is performed. The calculation of electric field gradient allow us to carry out a good interpretation of Mössbauer spectra for Fe-C and Fe-N systems.

Iron nitride Fe 4 N is studied by full-potential LAPW method. Structure parameters, electronic and magnetic properties as well as hyperfine interaction parameters are obtained. We observe perfect agreement with experimental results. Hypothetical Fe 4 N structure was also calculated to study the influence of disordering effects on parameters of Mössbauer spectra. We performed detailed analysis of EFG formation on Fe nuclei including magnetization effects. We show that the formation of N-Fe-N local configuration is energetically favourable in nitrogen austenites.

Magneto-structural properties of films of diluted ferromagnetic alloys Ni x Cu 1−x in the concentration range 0.7 < x < 1.0 are studied experimentally. Films deposited by magnetron sputtering show partial phase separation, as evidenced by structural analysis and ferromagnetic resonance measurements. The phase diagram of the Ni x Cu 1−x bulk system is obtained using numerical theoretical analysis of the electronic structure, taking into account the inter-atomic exchange interactions. The results confirm the experimentally found partial phase separation, explain it as magnetic in origin, and indicate an additional metastable region connected with the ferromagnetic transition in the system.