Crystal and magnetic structure of antiferromagnetic HoAuGe

• Published in: Journal of physics. Condensed matter Vol. 13; no. 11; pp. 2593 - 2606
• Main Authors: Gibson, B J, Pöttgen, R, Schnelle, W, Ouladdiaf, B, Kremer, R K
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 19.03.2001; Institute of Physics
• Subjects: Alloys; Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Magnetic properties and materials; Metals. Metallurgy; Physics; Spin arrangements in magnetically ordered materials (including neutron and spin-polarized electron studies, synchrotron-source x-ray scattering, etc.); Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Antiferromagnetism; Gold alloys; Incommensurate phases; Neutron diffraction; Curie-Weiss law; Ternary alloys; XRD; Experimental study; Magnetic susceptibility; Specific heat; Germanium alloys; Interatomic distances; Holmium alloys; Rare earth alloys; Magnetic structure; Transition element alloys; Crystal structure
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/13/11/315

HoAuGe was prepared from the elements by arc melting and subsequent annealing at 1070 K. Its crystal structure was refined from single-crystal x-ray diffractometer data: a = 440.10(5) pm, c = 723.26(9) pm, V = 0.1213(1) nm exp 3 , wR2 = 0.0640, 225 F exp 2 -values and ten variables. The nuclear structure was confirmed by neutron powder diffraction. HoAuGe adopts the NdPtSb-type structure. The gold and germanium atoms form two-dimensional infinite [AuGe] polyanions with intralayer Au-Ge distances of 260.5 pm, while the interlayer Au-Ge distances of 304.1 pm are much longer. The polyanions are separated by the holmium ions. Magnetic susceptibility, specific heat capacity and neutron diffraction measurements reveal antiferromagnetic ordering at T sub N = 5.6(2) K with further magnetic reordering at T sub 1 = 3.5(2) K and T sub 2 = 2.4(2) K. At higher temperatures Curie-Weiss behaviour is observed with mu sub eff exp exp = 10.2(2) mu sub B and Theta sub p = 0(1) K. From the magnetic specific heat a fourfold-degenerate ground state is found. The magnetic structure at 1.3 K is described by the propagation vector k = (1/2, 0, 0) with the Ho spins oriented within the bc-plane. As the temperature increases towards T sub N , the magnetic structure becomes incommensurate, which accounts for the observed additional transitions below T sub N .