Low-magnetic moment and strong anisotropy in non-doped iron-based superconductors

Machida, Masahiko  ; Nakamura, Hiroki  

We perform first-principles calculations with a LDA+U scheme for non-doped iron based superconductor LaFeAsO, which exhibits the antiferromagnetic ordering with an unexpected low magnetic moment compared to the one predicted by the standard first-principles calculation. Consequently, we find two stable electronic structures, one of which has the high magnetic moment 2.0 equivalent with the previous standard calculation results, and another of which reproduces the low magnetic moment 0.3 as obtained experimentally. The former is more stable in =0, whereas the latter becomes preferable in an intermediate range. Moreover, the latter well explains anomalous features such as in-plane high anisotropy in magnetic excitation and transport as observed experimentally.