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Degenerate hubbard model in a magnetic field. Application to Jahn‐Teller systems
Author(s) -
Khomskii D. I.,
Kugel K. I.
Publication year - 1977
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2220790206
Subject(s) - degenerate energy levels , condensed matter physics , jahn–teller effect , hubbard model , ground state , magnetic moment , physics , ferromagnetism , isotropy , magnetic field , ion , quantum mechanics , superconductivity
The Hubbard model in the strong coupling limit is used to study the behaviour of substances containing ions with orbitally degenerate ground state (Jahn‐Teller ions) in a magnetic field. In such substances the orbital occupancy and the magnetic structure appear to be closely connected. It is shown that in these systems a transition of first order may occur between different anti‐ferromagnetic phases as well as jumplike spin‐flip transitions (even for an isotropic exchange interaction S i S j ). The field dependence of the magnetic moment may be nonlinear, typical of meta‐magnetic substances. Both a simple model problem and a specific case of pervoskites with Jahn‐Teller ions (such as KCuF 3 ) are studied. The behaviour of quasi one dimensional systems is also considered.