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arXiv · 1906.00169

Magnetism in spin crossover systems: short-range order and effects beyond the Heisenberg model

V. I. Kuz'min·Yu. S. Orlov·A. E. Zarubin·T. M. Ovchinnikova·S. G. Ovchinnikov
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Abstract

To study non-Heisenberg effects in the vicinity of spin crossover in strongly correlated electron systems we derive an effective low-energy Hamiltonian for the two-band Kanamori model. It contains Heisenberg high-spin term proportional to exchange constant as well as low-spin term proportional to spin gap parameter $\varepsilon_s$. Using cluster mean field theory we obtain several non-Heisenberg effects. Near critical value of spin gap $\varepsilon^c_s$ there is a magnetic phase transition of first order. In the vicinity of $\varepsilon^c_s$ in the paramagnetic phase we observe non trivial behavior of the Curie constant in the paramagnetic susceptibility in the wide range of temperature. Reentrant temperature behavior of nearest-neighbor spin-spin correlations is observed at $\varepsilon_s > \varepsilon^c_s$. Finally, pressure-temperature magnetic phase diagram for ferroperriclase is obtained using the effective Hamiltonian.

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V. I. Kuz'min, Yu. S. Orlov, A. E. Zarubin, T. M. Ovchinnikova, S. G. Ovchinnikov. 2019-10-10. Magnetism in spin crossover systems: short-range order and effects beyond the Heisenberg model. https://doi.org/10.1103/physrevb.100.144429

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