Comparative study of the electronic and magnetic properties of BaFe${}_{2}$As${}_{2}$ and BaMn${}_{2}$As${}_{2}$ using the Gutzwiller approximation

Comparative study of the electronic and magnetic properties of BaFe $_{2}$ As $_{2}$ and BaMn $_{2}$ As $_{2}$ using the Gutzwiller approximation

Y. X. Yao, J. Schmalian, C. Z. Wang, K. M. Ho, and G. Kotliar

Phys. Rev. B 84, 245112 – Published 13 December 2011

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 3 $d$ orbitals together with the Ba 5 $d$ and As 4 $p$ 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 the LDA + Gutzwiller method with electron density self-consistency. The renormalization factors for the correlated Mn 3 $d$ 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 4 $p$ electrons to the correlated Fe/Mn 3 $d$ electrons is evident by the systematic shift of the results to the 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 the same values of the electron correlations closer to the transition to a Mott insulating state than BaFe $_{2}$ As $_{2}$ . Here an orbitally selective Mott transition, required for a system with close to six electrons, only occurs at significantly larger values for the Coulomb interactions.

Received 13 September 2011

DOI:https://doi.org/10.1103/PhysRevB.84.245112

Authors & Affiliations

Y. X. Yao

Ames Laboratory–US DOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA

J. Schmalian

Ames Laboratory–US DOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA and Karlsruhe Institute of Technology, Institute for Theory of Condensed Matter, D-76131 Karlsruhe, Germany

C. Z. Wang and K. M. Ho

Ames Laboratory–US DOE and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA

G. Kotliar

Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA

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Vol. 84, Iss. 24 — 15 December 2011

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