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 TN = 100 K for Gd3Ni, TN = 112 K for Gd3Rh to TC = 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.