Melnyk I. Features of Temperature-Concentration Dependences of Electrical Resistance and Short-Range Magnetic Order of Fe-Co Alloys

Українська версія

Thesis for the degree of Candidate of Sciences (CSc)

State registration number

0409U000827

Thesis Registration Form

0409U000827.pdf

Applicant for

Specialization

  • 01.04.07 - Фізика твердого тіла

23-02-2009

Specialized Academic Board

Д 26.001.23

Taras Shevchenko National University of Kyiv

Essay

Within the scope of the method of the cluster expansion for Green's functions and thermodynamic potential of a disordered crystal system the contributions from static and dynamic fluctuations of charge and spin densities are separated. An influence of the temperature, atomic and magnetic orders on the electronic structure and static conductivity of disordered b.c.c.-Fe Co alloys is investigated. The nature of weak temperature dependence of the electroresistance of b.c.c. Fe0.5Co0.5 and Fe0.88Co0.12 alloys as well as the microscopic mechanism of magnetic ordering in Fe0.5Co0.5 alloy, which are concerned with both the Fermi-level position inside the Coulomb quasi-gap region in electron energy spectrum and the realignment of this spectrum with a rise in temperature, are ascertained. As shown, the nonmonotonic concentration dependence of Fe-Co-alloy electroresistance is caused by the strong electron correlations and the magnetic order resulting from these correlations.

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