Ł. Gondek

Neutron diffraction and magnetisation studies of magnetic ordering in RAuIn (R=Tb, Dy, Ho)

Abstract Polycrystalline samples of the RAuIn (R=Tb, Dy, Ho) compounds have been prepared and studied by powder neutron diffraction and magnetisation measurements. These compounds crystallise in the hexagonal ZrNiAl-type structure. They have been found to be antiferromagnets with the Neel temperatures equal: 35 K (R=Tb), 11 K (R=Dy) and 4.8 K (R=Ho). At T=1.5 K the magnetic ordering of TbAuIn and DyAuIn is described by the propagation vector k =(0, 0, 1 2 ) while in the case of HoAuIn by two propagation vectors: k 1 =(0, 1 2 , 1 2 ) and k 2 =(0, 0, 1 2 ). Between T N and T SG =58 K spin-glass behaviour is reported for TbAuIn. For the first time, the two-step magnetic phase transition: From the long-range antiferromagnetic order through a spin-glass-like short-range ordering to a paramagnetic state is experimentally evidenced in this compound.

Crystal and magnetic structure of CeCu0.86Ge2

Abstract Neutron diffraction measurements have been performed on CeCu 0.86 Ge 2 at low temperatures. The compound crystallises in the orthorhombic CeNiSi 2 -type of structure (space group Cmcm ). The crystal structure parameters have been refined on the basis of the neutron diffraction pattern collected at T =20 K (paramagnetic region). Below the Neel temperature equal to 16.5 K a collinear antiferromagnetic ordering is present with the Ce magnetic moments aligned along the c -axis. The Ce magnetic moments equal to 1.85(4) μ B located in the crystal unit cell are coupled in a S 1 + S 2 − S 3 − S 4 sequence (C model type).

Thermal dependence of the lattice constants of LaAgSb2

The results of neutron diffraction measurements as a function of temperature are analyzed. An anomalous temperature dependence of the lattice constant c and some interatomic distances is observed. This result indicates a change in the interactions between the atoms, especially those near the lanthanum atom.