Magnetic structure of Er5Si4

As part of our ongoing study of giant magnetocaloric compounds, we have determined the magnetic structure of Er5Si4 by high-resolution neutron powder diffraction, ac-susceptibility, and Er-166 Mossbauer spectroscopy. The crystal space group is orthorhombic Pnma and the magnetic space group is Pn(')ma('). The magnetic ordering temperature is 32(3) K and the magnetic structure is characterized by ferromagnetic order of the three Er sites (4c, 8d(1), and 8d(2)) along [010], together with antiferromagnetic order of the 8d sites in the perpendicular (010) plane. The Er 4c magnetic mode is F-Y and the 8d magnetic mode is C(X)(+)F(Y)(+)G(Z)(+). At 3.6 K, the Er magnetic moments are 7.4(1), 6.9(2), and 7.6(2) mu(B) at the 4c, 8d(1), and 8d(2) sites, respectively, and the corresponding Er-166 hyperfine magnetic fields, at 5 K, are 715(5), 627(2), and 736(3) T. The neutron diffraction data show tentative evidence of a reorientation of the magnetic structure, most likely involving the development of an antiferromagnetic component at the 4c site, between 14 and 4 K. (C) 2004 American Institute of Physics.