Origin of spiral-spin order:back to origin Role of NNN anisotropic SE interaction 150 (a) =0 125 G 2a )J2=0.5J2 100.00 100 75 50 A 25 Tb 0 20 40 60 80 10020 40 60 80 100 J2(0.001) Role of NNN anisotropic SE interaction Origin of spiral-spin order: back to origin