Anomalous structural and dynamic properties in systems based on fand d-elements
A wide range of neutron and synchrotron methods have been used to study several systems in which anomalous physical properties are formed due to the interplay of local and collective degrees of freedom of the electron and phonon subsystems: EuCu2SixGe2-x, CeNi, FeSi, high-temperature superconductors- cuprates. A record volume collapse of the 4f-electron shell by 21% was observed in the intermediate- valence system CeNi, which exceeds the previous world record related to the gammaalpha transition in cerium with the volume collapse by 14-15%. The partial contribution of the iron ions to the phonon spectrum in FeSi was obtained. Anomalous anharmonicity of the vibrations of oxygen in the CuO2 plane was observed in the cuprates with both hole and electron dopings. The relation between the valence fluctuations of the Eu ions and the formation of the antiferromagnetic and Kondo-like ground states effect was established.