Origin of spiral-spin order:picture 3.0 paramagnetic A-AFM (b) 2.5 4x4X4 1/ 172/11 C-AFM 2/15 bic lattice 3/16 2.0 4/19 1/1 FMY 1/5 <1.5 O q=0 1/8 1/6 q=1/4 1.0 ferromagnetic downFdown FM/OD E-AFM 0.0 ,/(-J)1.0 0.5 1.5 0.5 0.0 5 0.00.10.2 0.30.40.50.6 JAF Kimura,Ishihara et al. Hotta et al. PRB68,060403R)(2003) PRL90,247203(2003) Origin of spiral-spin order: picture Kimura, Ishihara et al. PRB68, 060403(R) (2003) Hotta et al. PRL 90, 247203 (2003)