Journal of Alloys and Compounds 403 (2005) 71–75 The magnetic structure of TlCrTe 2 Sabina Ronneteg a,∗ , Marck-Willem Lumey b , Richard Dronskowski b , Rolf Berger a a Department of Materials Chemistry, Uppsala University, Box 538, SE-751 21 Uppsala, Sweden b Institut f ¨ ur Anorganische Chemie, Rheinisch-Westf¨ alische Technische Hochschule, Landoltweg 1, D–52056 Aachen, Germany Received 30 April 2005; accepted 18 May 2005 Available online 1 August 2005 Abstract The magnetic structure of the antiferromagnetic layer compound TlCrTe 2 has been determined by neutron powder diffraction. The magnetic moments on chromium are aligned along the c axis in the hexagonal cell and couple ferromagnetically within the sheets. Adjacent layers couple antiferromagnetically below the transition temperature of 145 K. This gives rise to a doubling of the c axis for describing the magnetic unit cell. The magnetic moment of the chromium atom is 3.39(4) μ B at 10 K in line with localised 3d 3 of Cr 3+ . Electronic structure calculations on TlCrTe 2 of density–functional type (GGA) show a clear driving force for the ferromagnetic coupling in the layers and a lowering of the total energy upon magnetic ordering, the theoretical magnetic moment being in almost quantitative agreement with the experiment. © 2005 Elsevier B.V. All rights reserved. Keywords: Magnetic measurements; Neutron diffraction; Magnetically ordered material; First principle calculations 1. Introduction Layered magnetic structures consist of metal sheets sepa- rated by non-magnetic atoms. Depending on atom kind and the distance between the magnetic layers the spins may cou- ple cooperatively in various ways. An example of a layered magnetic structure is the hexagonal TlCrTe 2 phase (P ¯ 3m1 nr 164, a = 4.016 ˚ A, c = 7.927 ˚ A) [1]. Here only the chromium ion possesses a magnetic moment at low temperature. The structure can be described as related to the NiAs-type (see Fig. 1), where the chromium and thallium atoms share the nickel position in an ordered manner. The tellurium atoms are at the arsenic positions, with a z parameter allowing for the difference in radius between Tl and Cr. The structure is the same as for LiTiX 2 (X = S, Se and Te) [2,3] and AgTiTe 2 [4,5], alternatively described as Li/Ag ions having been intercalated in the van der Waals gap between the X-ions in the titanium dichalcogenide framework (CdI 2 - type). There also exist other 1:1:2 chalcogenide structures where the stacking sequence of the non-metal is based on mainly ccp instead, which results in longer c axes [6–9]. ∗ Corresponding author. Tel.: +46 18 4713764; fax: +46 18 513548. E-mail address: sabro@mkem.uu.se (S. Ronneteg). TlCrTe 2 was reported as being antiferromagnetic (T N = 140 K) with a positive Curie–Weiss temperature (91 K) [9], however without details of the spin orientation. Antiferromagnetic-layered structures can exhibit very unex- pected magnetic structures as found for the case of TlCo 2 Se 2 [10]. Magnetic frustration often occurs in close-packed lay- ers if the magnetic moment lies in the plane. Several ternary chromium dichalcogenides (with another stacking of the lay- ers compared to TlCrTe 2 ) are antiferromagnetic and have a positive Curie–Weiss temperature. The magnetic struc- tures may nevertheless differ. In NaCrSe 2 and KCrS 2 , the magnetic structure consists of ferromagnetic layers (moment perpendicular to the c axis) with moments antiferromagneti- cally arranged to adjacent layers [7,8,11]. In contrast to this, AgCrSe 2 and NaCrS 2 also have the moment perpendicular to the c axis, but here an antiferromagnetic helical structure is formed [7,8]. The anisotropy of the structure is reflected in the magnetic behaviour. For instance, antiferromagnetic NaCrSe 2 and KCrSe 2 prove to have meta-magnetic proper- ties [12]. In this paper the TlCrTe 2 structure was studied by pow- der neutron diffraction and electronic structure calculations from first principles to investigate the details of the magnetic structure. 0925-8388/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jallcom.2005.05.028