Magnetic ordering in Th3P4-type Tb4Sb3 compound

The nature of the magnetic ordering of Tb₄Sb₃ compound (Th₃P₄-type, cubic; cI28, space group , No. 220, a = 0.91518(7) nm) has been investigated by using the techniques of magnetization and neutron diffraction. AC and DC magnetisation measurements indicate antiferromagnetic ordering at 108 K in zero magnetic field that is accompanied by a field-induced metamagnetic transition to a ferromagnetic state, in fields above 0.3 T. Neutron diffraction experiment in zero applied magnetic field shows that below T_N = 112(4) K Tb₄Sb₃ exhibits an antiferromagnetic flat spiral-type ordering with propagation vector K₁ = ±1/8, ±1/8, ±1/8]. The magnetic moment of Tb atoms is found to be M_Tb = 6.7(3) μ_B at 80 K. The magnetic moment of Tb atoms lie in the (1 1 1) plane of Tb₄Sb₃ unit cell (the cone axis arranges along 1 1 1] direction with cone angle β = 90°). Below T_N2  50 K, Tb₄Sb₃ shows second antiferromagnetic transition with K₂ = 1/2, 1/2, 1/2] with possible re-orientation of Tb magnetic moments.