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arXiv · 2105.09239

Origin of insulating ferromagnetism in iron oxychalcogenide Ce$_2$O$_2$FeSe$_2$

Ling-Fang Lin·Yang Zhang·Gonzalo Alvarez·Adriana Moreo·Elbio Dagotto
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Abstract

An insulating ferromagnetic (FM) phase exists in the quasi-one-dimensional iron chalcogenide Ce$_2$O$_2$FeSe$_2$ but its origin is unknown. To understand the FM mechanism, here a systematic investigation of this material is provided, analyzing the competition between ferromagnetic and antiferromagnetic tendencies and the interplay of hoppings, Coulomb interactions, Hund's coupling, and crystal-field splittings. Our intuitive analysis based on second-order perturbation theory shows that large entanglements between doubly-occupied and half-filled orbitals play a key role in stabilizing the FM order in Ce$_2$O$_2$FeSe$_2$. In addition, via many-body computational techniques applied to a multi-orbital Hubbard model, the phase diagram confirms the proposed FM mechanism, in agreement with experiments.

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Ling-Fang Lin, Yang Zhang, Gonzalo Alvarez, Adriana Moreo, Elbio Dagotto. 2021-08-13. Origin of insulating ferromagnetism in iron oxychalcogenide Ce$_2$O$_2$FeSe$_2$. https://doi.org/10.1103/physrevlett.127.077204

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