Successive magnetic ordering of the Tb sublattices in Tb3Pd20Si6

The chemical and magnetic structures of the intermetallic compound Tb3Pd20Si6 were studied by means of bulk magnetic measurements and neutron diffraction. The crystal structure of Tb3Pd20Si6 was confirmed to be isotypic with that of Ce3Pd20Si6, space group Fm (3) over bar m, No 225, with Tb being located at the two crystallographic sites 4a and 8c. The compound undergoes two successive second-order magnetic phase transitions at the Neel temperatures T-N1 = 10.2 K and T-N2 = 4.1 K Below T-N1, the 8c sites order in an antiferromagnetic sequence with a magnetic propagation vector k(1) = [1, 1, 1], leaving the 4a sites disordered down to T-N2, where additional antiferromagnetic ordering of the 4a sites sets in according to k(2) = [0, 0, 1].