Crystal and magnetic structure of TbFe0.25Ge2 compound

The crystal and magnetic structure of polycrystalline TbFe0.25Ge2 sample have been determined. X-ray and neutron diffraction studies indicate that this compound has the orthorhombic CeNiSi2-type crystal structure (space group Cmcm). The magnetic ordering, based on the neutron diffraction data in low temperature, is described by two components: a collinear antiferromagnetic G-type and a cosine-wave modulated one. In the collinear G-type structure the Tb magnetic moment is equal to 3.81(5) µB and it is parallel to the c-axis. The modulated structure is described by the propagation vector k=(0.460(8), 0, 0.305(1)), the Tb magnetic moment equals 7.75(8) µB, lies in b-c and forms an angle 23(2)° with the c-axis. The collinear component decreases to zero at 22.6 K while the modulated one at 190.8 K.