Microscopic origin of isotropic non-Heisenberg behavior in highly correlated systems

Abstract

We have reanalyzed the microscopic origin of the isotropic deviations that are observed from the energy spacings predicted by the 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 non-Hund states which brought the most important contribution to the deviations. For systems containing more than two magnetic centers, non-Hund 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.

4 pages, 3 figures

References in corpus (3)

• The quadrupolar phases of the S=1 bilinear-biquadratic Heisenberg model on the triangular lattice
• Spin nematic correlations in bilinear-biquadratic S=1 spin chains
• Possible ferro-spin nematic order in NiGa2S4

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