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Abstract

GdPdCd was obtained in pure form via reaction of the elements in a sealed tantalum tube in a high-frequency furnace. The structure was investigated by X-ray diffraction on both powders and single crystals: ZrNiAl type, P (6) over bar 2m, a = 758.2(1), c = 391.78(7) pm, wR(2) = 0.0410 for 358 F-2 values and 14 variables. Striking structural motifs of GdPdCd are two types of palladium-centered tricapped trigonal prisms [PdlCd(3)Gd(6)] and [Pd2Cd6Gd3]. Together the palladium and cadmium atoms build a three-dimensional network in which the gadolinium atoms fill distorted pentagonal channels. Susceptibility measurements reveal Curie-Weiss behaviour with an effective magnetic moment of 8.2(1) mu(B)/Gd. GdPdCd orders ferromagnetically at T-C = 62.5 (5) K and shows a saturation magnetization of 7.3 (1) mu(B)/Gd at 4.2 K and 5 T. The thermal variations of hyperfine parameters in GdPdCd were measured over the temperature ran-e from 4.2 to 67 K using Gd-155 Mossbauer spectroscopy. The change of the electric field gradient below the Curie temperature T-C is interpreted by an anomalous thermal expansion associated with magnetostrictive strains. The electronic and magnetic properties of GdPdCd were investigated by TB-LMTO-ASA band structure calculations. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.