Magnetic states of iron-based superconducting compounds calculated by using GGA+U method with negative U

2014/07/19 by Jang, Jae Kyung, Rhee, Joo Yull
#FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Strongly Correlated Electrons (cond-mat.str-el)

paper · doi:10.48550/arxiv.1407.5137

Abstract

The magnetic moments per Fe atom in high-T_\textrmc iron-based superconducting compounds, BaFe₂As₂ and LaFeAsO obtained from the first-principles calculation with local-spin-density approximation are much larger than those obtained from experiments. To resolve the contradictory results between theory and experiment we employed the so-called LDA+ U (or more exactly GGA+ U) technique with negative U in the first-principles calculation. The calculated values with negative U, - 0.09 Ry and - 0.10 Ry for BaFe₂As₂ and LaFeAsO, respectively, are in excellent agreement with the experimental ones. By comparing the differences in d-orbital occupation numbers and spin densities calculated by using a simple GGA and GGA+ U with negative U, the magnetic moments of the two compounds are found to be similar to the case of low-spin state of metamagnetic Fe₃Al alloy.

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