Journal of Alloys and Compounds 400 (2005) 16–22 Hyperfine interactions studied by 119 Sn M ¨ ossbauer spectroscopy in TbAuSn and TmAuSn compounds K. L ˛ atka a,∗ , J. Gurgul b , R. Kmie´ c c , A.W. Pacyna c , W. Chajec d a Marian Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krak´ ow, Poland b Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Krak´ ow, Poland c H. Niewodnicza´ nski Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342 Krak´ ow, Poland d Institute of Physics, Cracow University of Technology, Podchor˛ a˙ zych 1, 30-084 Krak´ ow, Poland Received 25 February 2005; received in revised form 16 March 2005; accepted 21 March 2005 Available online 10 May 2005 Abstract X-ray diffraction, magnetic susceptibility measurements and 119 Sn M¨ ossbauer spectroscopy were used to study structure and hyperfine interactions in intermetallic TbAuSn and TmAuSn compounds. It was shown that the first compound orders antiferromagnetically at low temperatures with Tb magnetic moments inclined at an angle of about 25 ◦ to the crystallographic c-axis. The second compound stays non- magnetic in the whole measured region. The occurrence of a magnetic hyperfine field distribution in TbAuSn suggests that this compound crystallizes in the disordered CaIn 2 -type of structure. © 2005 Elsevier B.V. All rights reserved. Keywords: X-ray and -ray spectroscopies; Magnetically ordered materials; Magnetic measurements 1. Introduction The intermetallic compounds RAuSn (R – rare earth ele- ment) form a group of materials, which demonstrate a large variety of physical phenomena [1]. These properties are re- lated to the hybridization between the rare earth 4f-electron states and the conduction electron states. Many of the RAuSn compounds order magnetically at low temperatures showing complex structures due to interplay between magnetic inter- actions and crystal field effects [2–9]. The RAuSn compounds belong to a class of materials, which crystallize in the hexagonal CaIn 2 -type of structure (or its ordered variant LiGaGe-type) for the light rare earth elements and in the cubic MgAgAs-type of structure for the heavy rare earth elements. Both types of crystal structures were found to exist in the HoAuSn and ErAuSn compounds [10,11]. Neutron diffraction experiment has revealed that TbAuSn orders magnetically with T N = 15 K [5]. Below T N this com- ∗ Corresponding author. Tel.: +48 12 6635668; fax: +48 12 337086. E-mail address: uflatka@cyf-kr.edu.pl (K. L ˛ atka). pound exhibits a collinear antiferromagnetic order described by the wave vector  k = [1/2, 0, 0] with magnetic moments normal to the c-axis. In this paper, we present the results of magnetic and spec- troscopic studies on the TbAuSn and TmAuSn compounds. 119 Sn M¨ ossbauer spectroscopy, as a microscopic technique, was applied to characterise the local electronic properties of both compounds and was used to monitor the temperature evolution of the transferred hyperfine magnetic field H hf at the diamagnetic tin ions. This method is also sensitive enough to get insight into possible crystallographic order of Au and Sn ions over the “In” sites within the CaIn 2 -type of structure [4]. 2. Experimental Samples of TbAuSn and TmAuSn were prepared by arc- melting of the pure components in the stoichiometric ratio under a purified argon atmosphere and were subsequently an- nealed in evacuated silica tube at 773 K for 1 week. Melting was performed several times to maximize homogeneity of the samples. Powder X-ray analyses were carried out using 0925-8388/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2005.03.061