Two successive magnetic phase transitions in Dy 3Pd 20Si 6 studied by neutron powder diffraction

Abstract

The low-temperature magnetic structures of Dy 3Pd 20Si 6 have been studied by neutron powder diffraction. In the cubic crystal structure of Dy 3Pd 20Si 6 (space group Fm 3 ̄ m), the Dy ions occupy the sites 8c and 4a. They undergo two second-order successive magnetic phase transitions at the Néel temperatures T N1≈5.8 K and T N2≈1.8 K, respectively. Between T N1 and T N2, antiferromagnetic ordering of only the 8c sites occurs with k 1 =[1, 1, 1], whereas the 4a sites are disordered. Below T N2, an additional ordering of the 4a sites sets in with k 2 =[0, 0, 1]. Unlike the situation found for Tb 3Pd 20Si 6 and Nd 3Pd 20Ge 6, the 4a magnetic Dy moments in Dy 3Pd 20Si 6 point along an intermediate direction close to the high symmetry axis [1, 1, 1].