Microscopic origin of isotropic nonHeisenberg behavior in S=1 magnetic systems
Abstract
We have reanalyzed the microscopic origin of the isotropic deviations that are observed from the energy spacings predicted by the Heisenberg Dirac van Vleck (HDVV) Hamiltonian. Usually, a biquadratic spin operator is added to the HDVV Hamiltonian to account for such deviations. It is shown here that this operator cannot describe the effect of the excited atomic nonHund states which brought the most important contribution to the deviations. For systems containing more than two magnetic centers, nonHund states cause additional interactions that are of the same order of magnitude as the biquadratic exchange and should have significant effects on the macroscopic properties of extended systems.
 Publication:

Physical Review B
 Pub Date:
 October 2007
 DOI:
 10.1103/PhysRevB.76.132412
 arXiv:
 arXiv:0706.3353
 Bibcode:
 2007PhRvB..76m2412B
 Keywords:

 75.10.b;
 71.10.w;
 71.15.m;
 71.27.+a;
 General theory and models of magnetic ordering;
 Theories and models of manyelectron systems;
 Methods of electronic structure calculations;
 Strongly correlated electron systems;
 heavy fermions;
 Condensed Matter  Strongly Correlated Electrons
 EPrint:
 4 pages, 3 figures