First-principle electronic structure calculations for magnetic moment in iron-based superconductors; An LSDA + negative U study

Nakamura, Hiroki  ; Hayashi, Nobuhiko; Nakai, Noriyuki; Okumura, Masahiko   ; Machida, Masahiko  

In order to resolve a discrepancy of the magnetic moment on Fe between the experimental and calculation results, we perform first-principle electronic structure calculations for iron-based superconductors LaFeAsOF in which and by using the LSDA+ framework. Consequently, we confirm in both the mother and doped compounds that negative correction is crucial in matching the calculated magnetic moment with the observed one. A reason of the negative correction is that the Coulomb interaction on Fe orbitals is unexpectedly screened than LSDA's expectation. We discuss which type of situation emerges when the negative is a good correction in these compounds.