Investigation of the magnetocaloric effect in correlated metallic systems with Van Hove singularities in the electron spectrum

• Published in: Physics of metals and metallography Vol. 118; no. 3; pp. 207 - 216
• Main Authors: Igoshev, P. A., Kokorina, E. E., Nekrasov, I. A.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01.03.2017; Springer Nature B.V
• Subjects: Chemistry and Materials Science; Correlation; Electrical and Magnetic Properties; Electronics; Entropy; Lattices; Magnetic fields; Materials Science; Mathematical analysis; Mathematical models; Metallic Materials; Singularities; magnetocaloric effect; correlated metals; Van Hove singularities
• ISSN: 0031-918X; 1555-6190
• DOI: 10.1134/S0031918X17030048

In this work, the magnetic contribution to the isothermal entropy change Δ S upon switching on a magnetic field has been investigated in correlated metallic ferromagnets within the Hubbard nondegenerate model. The analytical expression Δ S for obtained in the mean-field approximation depends substantially on the electronic structure (density of electron states), which presents new ways to increase the absolute value of Δ S relative to the known result obtained within the Heisenberg model. The temperature dependence of Δ S has been calculated at different values of the Coulomb interaction U and the number of electrons n for the Bethe infinite-dimensional lattice and square lattice with allowance for transfer integrals in the first ( t ) and the second ( t ') coordination shells. It has been found that the presence of Van Hove singularities in the electronic spectrum near the Fermi level makes it possible to considerably increase |Δ S | at a fixed magnetic field. The possibility of first-order magnetic phase transitions depending on the model parameters has been analyzed.