TEMPERATURE DEPENDENCE OF LATTICE PARAMETRES FOR Gd₃T
(T = Ni, Rh, Ir)

J. Kusz¹, E.Talik¹, H. Böhm²

¹Institute of Physics, University of Silesia, Uniwersytecka 4, 40 007 Katowice, Poland, e-mail: kusz@us.edu.pl
²Institut für Geowissenschaften der Universität Mainz, Saarstr. 55099 Mainz, Germany

Keywords: rare earth - transition metal compounds, lattice parameters, spontaneous magnetostriction

Gd₃Ni, Gd₃Rh and Gd₃Ir crystallize in the orthorhombic Fe₃C - type crystal structure which belongs to the Pnma space group [1]. In this structure Gd atoms are situated in the vertices of the trigonal prisms (the 4c and 8d positions in Wyckoff notation), whose centres are occupied by the transition metal 3d (Ni), 4d (Rh) and 5d (Ir) in the 4c position. Magnetic measurements of Gd₃T revealed the increase of the ordering temperature from T_N = 100 K for Gd₃Ni, T_N = 112 K for Gd₃Rh to T_C = 155 K for Gd₃Ir [2,3].

The single crystals of Gd₃Ni, Gd₃Rh and Gd₃Ir were obtained by the Czochralski method from a levitated melt using high purity starting materials. Temperature dependence of lattice parameters and unit cell volume were measured for Gd₃Ni, Gd₃Rh and Gd₃Ir single crystals in the range of 10 - 300K using the graphite - monochromatized Cu K radiation (Enraf - Nonius Rotating Anode) and a four - circle Huber diffractometer, with a two-stage closed - cycle helium low temperature attachment (CTI - Cryogenics). The anisotropic character of the thermal variations of lattice parameters and an anomalous expansion around the Nel temperature is a consequence of the spontaneous magnetostriction accompanied by the magnetic ordering of the gadolinium moments.

1. Landolt - Börnstein, III/19d2, Magnetic Properties of Metals (Springer-Verlag, Berlin, 1989) p.26.
2. E.Talik and A. Olebarski, J. Alloys and Compounds 223 (1995) 87.
3. E. Talik and M. Neumann, J. Magn. Magn. Mater. 140 -144 (1995) 795.