Magnetic states of iron-based superconducting compounds calculated by using GGA$+U$ method with negative \emph{U}

Jae Kyung Jang; Joo Yull Rhee

paper

Magnetic states of iron-based superconducting compounds calculated by using GGA $+ U$ method with negative \emph{U}

arXiv:1407.5137

Abstract

The magnetic moments per Fe atom in high- $T_{c}$ iron-based superconducting compounds, BaFe $_{2}$ As $_{2}$ 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 \emph{U} in the first-principles calculation. The calculated values with negative \emph{U}, $- 0.09$ Ry and $- 0.10$ Ry for BaFe $_{2}$ As $_{2}$ and LaFeAsO, respectively, are in excellent agreement with the experimental ones. By comparing the differences in \emph{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 Fe $_{3}$ Al alloy.

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

Abstract

Magnetic states of iron-based superconducting compounds calculated by using GGA $+ U$ method with negative \emph{U}