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arXiv · 1109.2679

A comparative study of the electronic and magnetic properties of BaFe_2As_2 and BaMn_2As_2 using the Gutzwiller approximation

Y. X. Yao·J. Schmalian·C. Z. Wang·K. M. Ho·G. Kotliar
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Abstract

To elucidate the role played by the transition metal ion in the pnictide materials, we compare the electronic and magnetic properties of BaFe_{2}As_{2} with BaMn_{2}As_{2}. To this end we employ the LDA+Gutzwiller method to analyze the mass renormalizations and the size of the ordered magnetic moment of the two systems. We study a model that contains all five transition metal 3d orbitals together with the Ba-5d and As-4p states (ddp-model) and compare these results with a downfolded model that consists of Fe/Mn d-states only (d-model). Electronic correlations are treated using the multiband Gutzwiller approximation. The paramagnetic phase has also been investigated using LDA+Gutzwiller method with electron density self-consistency. The renormalization factors for the correlated Mn 3d orbitals in the paramagnetic phase of BaMn_{2}As_{2} are shown to be generally smaller than those of BaFe_{2}As_{2}, which indicates that BaMn_{2}As_{2} has stronger electron correlation effect than BaFe_{2}As_{2}. The screening effect of the main As 4p electrons to the correlated Fe/Mn 3d electrons is evident by the systematic shift of the results to larger Hund's rule coupling J side from the ddp-model compared with those from the d-model. A gradual transition from paramagnetic state to the antiferromagnetic ground state with increasing J is obtained for the models of BaFe_{2}As_{2} which has a small experimental magnetic moment; while a rather sharp jump occurs for the models of BaMn_{2}As_{2}, which has a large experimental magnetic moment. The key difference between the two systems is shown to be the d-level occupation. BaMn_{2}As_{2}, with approximately five d-electrons per Mn atom, is for same values of the electron correlations closer to the transition to a Mott insulating state than BaFe_{2}As_{2}. Here an orbitally selective transition, required for a system with close to six electrons only occurs at significantly larger values for the Coulomb interactions.

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Y. X. Yao, J. Schmalian, C. Z. Wang, K. M. Ho, G. Kotliar. 2011-09-13. A comparative study of the electronic and magnetic properties of BaFe_2As_2 and BaMn_2As_2 using the Gutzwiller approximation. https://doi.org/10.1103/physrevb.84.245112

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