Abstract
A review of fundamental works by Shubin and Vonsovsky on the formulation of the polar and s–d(f) exchange models is given. Their ideas are compared with subsequent developments in the theory of magnetism in d- and f-metals and their compounds. Modern approaches including various slave-boson and slave-fermion representations, formation of exotic quasiparticles etc. are discussed. Internal connections between different many-electron models (the Heisenberg, Hubbard, t–J, Anderson Hamiltonians) are presented. Description of anomalous rare-earth and actinide compounds (Kondo lattices, systems with heavy fermions and non-Fermi-liquid behavior) within the framework of the s–d(f) exchange model and related models is considered.
Highlights
Being formulated already in the first half of XX century, the polar and s–d(f) exchange models still work successfully in the solid state physics. They provide a basis for new theoretical concepts describing physical phenomena discovered by experimentators
The model approaches which include effects of strong electron correlations in d- and f-compounds turn out to be very useful from the point of view of the qualitative microscopic description
The spectrum of highly-correlated systems is often described in terms of auxiliary Fermi and Bose operators, which correspond to quasiparticles with exotic properties. Last time such ideas have been extensively applied in connection with the unusual spectra of high-Tc superconductors and heavy-fermion systems
Summary
The papers by S.P. Shubin and S.V. Vonsovsky on the polar model [1] put forward a program of building up a systematic theory of solids with account of electron correlations. Vonsovsky on the polar model [1] put forward a program of building up a systematic theory of solids with account of electron correlations Such a theory should explain simultaneously electric and magnetic properties of metals and combine localized and itinerant features of d-electrons. The s–d(f) exchange model [2] provided a basis to describe transport properties of transition 3dmetals and magnetism of 4f-metals. Later this model was applied to explain electronic properties of anomalous rare-earth and actinides compounds, including Kondo lattices and heavy-fermion systems.
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