Features of Dynamics of Atoms in Nanosize Surface Area of the Ferromagnetic 3d-Metal-Based Alloys

Abstract

This review work is dedicated to the 70th anniversary of the G.V. Kurdyumov Institute for Metal Physics of National Academy of Sciences of Ukraine (1945–2015). The review reports on the results of investigations of dynamic characteristics of the surface of ferromagnetic single-crystal Fe–Ni and Co–Ni alloys obtained in department of the surface atomic structure and dynamics. Interest in the study of the surface dynamic properties of the metals and alloys is caused by the fact that the explanation of many physical, chemical, and mechanical properties of the surface materials and their macroscopic behaviour is directly or indirectly associated with the consideration of the vibrational motion of the surface atoms. The developed new method for complex non-destructive layer-by-layer analysis with monolayer resolution allows studying the atomic structure, element composition, and dynamic characteristics (Debye temperature, mean-square displacements of atoms, the coefficient of thermal expansion and the force constants). The change of the interatomic forces occurring during the phase transformations in surface region of the ferromagnetic alloys it determined. Magnetic ordering causes significant changes of both harmonic and anharmonic components of interatomic interaction forces. In turn, this leads to changes of thermal expansion coefficient within the range of ferromagnetic Curie temperature and also to the appearance of a contribution to the dynamic characteristics. It is obvious that these changes in the surface differ from the crystal bulk due to the specific distribution of the interatomic interaction forces in the surface layers.

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