L Journal of Alloys and Compounds 334 (2002) 9–13 www.elsevier.com / locate / jallcom Single crystal study of the high-Curie-temperature ferromagnet Gd Sc Ge and of Gd Sc Ge 1.02 0.98 2.38 2.62 3 a, b a c c * P. Manfrinetti , M. Pani , A. Palenzona , S.K. Dhar , Surjeet Singh a INFM and Dipartimento di Chimica e Chimica Industriale, Via Dodecaneso 31, I-16146 Genova, Italy b Dipartimento di Chimica e Chimica Industriale, Via Dodecaneso 31, I-16146 Genova, Italy c CMP & MS, T.I.F.R., Homi Bhabha Road, Mumbai, 400 005, India Received 11 June 2001; accepted 26 June 2001 Abstract The title ternary compounds have been thoroughly studied by X-ray diffraction, both on powders and single crystals. The already reported GdScGe does not form exactly at the equiatomic composition but with a stoichiometry slightly richer in Gd: Gd Sc Ge; it 1.02 0.98 ˚ crystallizes with the tetragonal CeScSi-type (ordered La Sb-type, space group I4 / mmm) with a54.261(1) and c515.593(5) A. 2 ˚ Gd Sc Ge is hexagonal, Mn Si -type (space group P6 / mcm), with cell parameters a58.276(5) and c56.116(6) A. Magnetic 2.38 2.62 3 5 3 3 measurements show that Gd Sc Ge undergoes a ferromagnetic transition at T 5350 K, whilst no evidence of long range magnetic 1.02 0.98 c ordering has been detected for Gd Sc Ge from 1.5 to 60 K, as deduced by preliminary heat capacity data.  2002 Elsevier 2.38 2.62 3 Science B.V. All rights reserved. Keywords: Rare earth compounds; Crystal structure; X-ray diffraction; Magnetic measurements 1. Introduction In a recent work by Morozkin et al. [5], the equiatomic GdScGe and TbScGe compounds were reported to crys- We have recently reported a thorough investigation of tallize in the tetragonal La Sb-type structure, the same 2 the structural and magnetic properties of CeScSi and structure type adopted by all light rare earths analogues. CeScGe intermetallics [1] which have the tetragonal Morozkin et al. [5] found that GdScGe and TbScGe were CeScSi-type structure [2,3] (ordered ternary variant of the not completely single phase, the parasitic impurity phase La Sb-type) and order antiferromagnetically at 26 and 43 being identified as belonging to the hexagonal Ti Ga - 2 5 4 K, respectively. It was found that annealing at proper type; they explained the presence of this extra phase as the temperatures is essential to obtain single phase com- high-temperature modification of the equiatomic ternaries. pounds. The magnetic ordering temperatures of CeScSi Considering that the above data were obtained from and CeScGe are fairly high when compared with other powder data, and in order to obtain an accurate de- compounds of cerium with non-magnetic elements. This termination of the Gd–Gd and Gd–Sc bond lengths, we prompted us to study the magnetic properties of RScSi and deemed it suitable to undertake a single-crystal structural RScGe for R5Pr, Nd, Sm and Gd as one would expect analysis of GdScGe in our on-going investigation of the these compounds to order magnetically at much higher RScSi and RScGe compounds. In this work we report our temperatures on the basis of de Gennes scaling. An results on structural characteristics of GdScGe and additional motivation came from the recent work on Gd (Gd,Sc) Ge . The reason for preparing the second com- 5 3 based compounds which exhibit a large magnetocaloric pound will become obvious from what follows. A pre- effect making them promising materials for magnetic liminary study of the magnetic properties is also included. refrigeration [4]. 2. Experimental *Corresponding author. Tel.: 139-010-353-6081; fax: 139-010-362- 8252. E-mail address: chimfis@chimica.unige.it (P. Manfrinetti). Metals to prepare the alloys were commercial products 0925-8388 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0925-8388(01)01752-2