Journal of Alloys and Compounds 375 (2004) L1–L3 Letter Magnetic structure of ErT x Sn 2 (T = Co, Ni) compounds B. Penc a , E. Wawrzy´ nska a , A. Szytula a,∗ , A. Gil a , J. Hernandez-Velasco b , A. Zygmunt c a M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow, Poland b BENSC, Hahn-Meitner Institute, Glienicker Str. 100, D-14109 Berlin-Wannsee, Germany c W. Trzebiatowski Institute of Low Temperature and Structure Research, Okólna 2, 50-950 Wroclaw, Poland Received 30 October 2003; received in revised form 20 November 2003; accepted 20 November 2003 Abstract In this work, the magnetic properties and magnetic structure of the ErT x Sn 2 (T = Co, Ni) stannides are reported. These compounds crystallize in the orthorhombic CeNiSi 2 -type structure and are antiferromagnets with the Néel temperature equal to 4.7 K for ErCo 0.24 Sn 2 and 4 K for ErNi 0.15 Sn 2 . Neutron diffraction measurements indicate the presence of the collinear magnetic structure described by the propagation vector k = (0, 0, 1/2). © 2003 Elsevier B.V. All rights reserved. Keywords: Rare earth compounds; Antiferromagnets; Magnetic structure; Neutron diffraction 1. Introduction Ternary rare earth compounds of composition RT x X 2 , where R is a rare earth metal, T is a 3d element and X a p-electron element (Si, Ge, Sn) with the CeNiSi 2 -type struc- ture (Cmcm space group) [1] are a numerous family of com- pounds [2]. These compounds display a variety of magnetic behaviors that has been the subject of investigations for about 15 years [3]. They crystallize as stoichiometric (x = 1) or non-stoichiometric (0 <x< 1) compounds. The first group form silicides and some germanides [1], while the second one form germanides and stannides [2]. This work reports the results of magnetic and neutron diffraction measurements which have been carried out to de- termine magnetic properties as well as crystal and magnetic structures of ErT x Sn 2 (T = Co, Ni) compounds. 2. Experimental details and results The ErT x Sn 2 (T = Co, Ni) compounds were prepared from high-purity rare earth, cobalt or nickel and tin ele- ments, with the stoichiometry arising from the data in [2], ∗ Corresponding author. Tel.: +48-12-632-4888; fax: +48-12-633-7086. E-mail address: szytula@if.uj.edu.pl (A. Szytula). by arc melting in a purified argon atmosphere. The reaction products were annealed at 800 ◦ C for several days and then checked for purity by X-ray powder diffraction. The reflec- tions were indexed within the orthorhombic CeNiSi 2 -type structure. The determined lattice parameters are in good agreement with the data reported in [2]. Magnetization data were collected using a SQUID magnetometer in the tem- perature range from 1.8 to 15 K. Neutron diffractograms were obtained using the E6 instrument at the BER II reac- tor (Hahn-Meitner Institute, Berlin). The incident neutron wavelength was 2.448 Å. The diffraction patterns were col- lected at several temperatures between 1.5 and 15 K. The Rietveld-type program Fullprof [4] was used for processing the neutron diffraction data. The temperature dependence of magnetization in low magnetic fields (up to 75 Oe) recorded at low temperatures (see Fig. 1) shows the behavior typical for the phase transi- tion from an antiferromagnetic state to a paramagnetic state (at 4.7 K for ErCo 0.24 Sn 2 and 4 K for ErNi 0.15 Sn 2 ). The neutron diffraction patterns recorded in the paramag- netic state (at 15 K for ErCo 0.24 Sn 2 and ErNi 0.15 Sn 2 ) con- firm that both compounds have the orthorhombic crystal structure of the CeNiSi 2 -type. In this structure, all the atoms occupy the 4(c) position (0, y, 1/4) with different values of the positional parameter y. The values of the a, b and c lat- tice parameters as well as of the positional parameters y, corresponding to the minimum of the appropriate reliability factor, are listed in Table 1. 0925-8388/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2003.11.020