Magnetic Properties and Crystal Structure of Solidsolution

Phys. Status Solidi B 251, No. 5, 958–964 (2014) / DOI 10.1002/pssb.201350038 b solidi p status s s www.pss-b.com physica basic solid state physics Magnetic properties and crystal structure of solid-solution Cu2MnxFe1ÀxSnS4 chalcogenides with stannite-type structure F. López-Vergara*,1, A. Galdámez1, V. Manríquez1, P. Barahona2, and O. Peña3 1 Facultad de Ciencias, Departamento de Química, Universidad de Chile, Santiago, Chile 2 Facultad de Ciencias Básicas, Universidad Católica del Maule, Talca, Chile 3 Institut des Sciences Chimiques de Rennes, UMR 6226, Université de Rennes 1, Rennes, France Received 17 June 2013, revised 27 November 2013, accepted 7 January 2014 Published online 3 February 2014 Keywords chalcogenides, crystal structure, magnetic properties * Corresponding author: e-mail [email protected], Phone: þ56 (2) 2978 7267, Fax: þ56 (2) 2271 3888 New solid solutions Cu2MnxFe1ÀxSnS4 were prepared by direct with AF interactions, weaker by more than one order of combination of the corresponding elements at 850 8C. The magnitude compared to other diluted magnetic semiconductors crystal structure of Cu2Mn0.4Fe0.6SnS4 was determined by (DMSs) with zinc-blende or wurzite crystal structure. single-crystal X-ray diffraction. This phase is described in the space group I42 m where each cation is tetrahedrally coordinated to four sulfur anions in a sphalerite-like arrange- ment. The XRD patterns of the solid solutions Cu2Mnx- Fe1ÀxSnS4 were fully indexed in the space group I42m and the values of the cell parameter for all phases obey the usual linear Vegard behavior. A progressive evolution of the magnetic moment in the paramagnetic state is observed when increasing the content of manganese. The negative values of the Curie– Weiss constant, u, indicate an antiferromagnetic (AF) behavior ß 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 Introduction The diluted magnetic semiconductor Cd1ÀzMnzTe alloy, which shows spin-glass behavior, with (DMS) materials are of interest because of the dual character magneto-optical effects, bound magnetic polarons, etc. [5, 6]. of their properties. Thus, the semiconductor nature In the last decades, the investigations on DMS have been influences the optical properties of the material, useful for focused to the important family of quaternary chalcogenides M1þM2þM4þQ M1þ ¼ M2þ ¼ information processing, while the magnetic nature allows of 2 4 type, where Cu, Ag; Mn, massive storage of information. These materials have Fe, Co, Ni, Zn, Cd; M4þ ¼ Si, Ge, Sn, Pb, and Q ¼ S, Se, attracted renewed importance in recent years in the search Te [7–10]. The tetragonal crystal structure of these phases is to complement their properties, and booster potential based on zinc-blende or an orthorhombic superstructure for applications in optoelectronics and magnetic devices wurtzite (known as wurtz–stannite), where each cation is [1–4]. The DMS materials that have been the most studied tetrahedrally coordinated to four sulfur anions [11–14]. In are alloys derived from adamantane-type structures, where the quaternary chalcogenides takes place a reduction of each cation is coordinated to four anions and vice versa. symmetry, characterized by an increase in the degree of These materials can be obtained by isomorphic substitution freedom in the positions of the sulfide anion, going from zinc of a fraction of the group II cations, by paramagnetic ions blende (1/4, 1/4, 1/4) – chalcopyrite (x, 1/4, 1/8) – stannite 2þ 2þ 2þ such as Mn ,Fe ,Co , etc. An example is the (x, x, z) – kesterite (x, y, z). The phases Cu2FeSnS4 and ß 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Original Paper Phys. Status Solidi B 251, No. 5 (2014) 959 Cu2ZnSnS4 crystallize in the structures of stannite-type and nitrogen. The products appeared to be air- and moisture- kesterite-type, respectively [15]. stable over several weeks. The Cu2FeSnS4 stannite, a well-known sulfide mineral for its semiconductor properties, has been the focus of 2.2 Characterization Powder X-ray diffraction pat- different magnetic studies, in both mineral and its synthetic terns were collected, at room temperature, on Siemens materials, finding an antiferromagnetic (AF) behavior and an D5000 powder diffractometer, with Cu Ka radiation important magnetic anisotropy. Both, the magnetic anisot- (l ¼ 1.541871 Å) in the range 58 < 2u < 808. The X-ray ropy and exchange interactions are larger than those found in diffraction patterns were indexed with the computer program the analogous Mn-based material [8, 14]. There also has CHECKCELL. been an extensive characterization of the synthetic mineral The chemical compositions of the powder samples and Cu2MnSnS4 stannite-type, where an AF order at the Néel single crystal were determined by scanning electron temperature of 20 K has been reported thanks to magnetiza- microscopy with the aid of energy-dispersive X-ray analysis tion measurements and neutron-diffraction experiments, in (SEM-EDS) using a JEOL JXA 8600 electron microprobe addition, the neutron diffraction data showed an AF collinear (Table 1). The powder samples were compacted at structure [8]. 5 Â 108 Pa, resulting in cylindrical pellets, mounted onto It is known that the magnetic behavior, associated to the double-side carbon tape and adhered to an aluminum magnetic ions present in the structure, may modify the specimen holder. The EDS data were collected for 60 s using magnetic and optical properties of semiconductors. Thus, an accelerating voltage of 22.5 kV. through the use of alloys, the properties of the DMS Single-crystal X-ray diffraction data of Cu2Mn0.4- materials can be modulated by varying the cationic Fe0.6SnS4 were collected, at room temperature, on a Bruker composition to achieve specific requirements. Recently, it Kappa CCD diffractometer, using graphite-monochromat- has been suggested that quaternary chalcogenides can be ized Mo Ka radiation (l ¼ 0.71073 Å). The collection of good candidates for improper ferroelectricity [16]. intensity data was carried out with the program COL- We have previously reported the magnetic properties LECT [17]. Cell refinement and data reduction were carried and crystal structures of the a new family of out with Dirax/lsq and EvalCCD programs [18, 19]. Multi- Cu2Mn1ÀxCoxSnS4 chalcogenides with kesterite type struc- scan absorption correction was performed with SADABS ture, where both Cu2MnSnS4 and Cu2CoSnS4 end members program [20]. The structure was refined in full-matrix of the solid solutions crystallizes in the stannite space group least-squares using the SHELXL crystallographic package I42 m (no. 121) [15]. In this work, we report the synthesis, programs [21]. structural characterization, and magnetic properties of new Differential thermal analysis (DTA) and thermogravi- solid solutions Cu2MnxFe1ÀxSnS4 obtained from Cu2FeSnS4 metric analysis (TGA) were performed on a Simultaneous by replacing a fraction of the Fe2þ cations with the Thermal Analysis, NETZSCH STA 409. The DTA/TGA paramagnetic Mn2þ ion. The aim of this work is to study curves were run simultaneously on each sample from room the influence of such substitution and of the preparation temperature to 1000 8C, in flowing argon at a heating rate of method onto the magnetic properties of the quaternary 10 8C minÀ1. chalcogenide. Magnetic measurements were performed on pelletized powder samples using a Quantum Design MPMS XL5 2 Experimental SQUID magnetometer between 2 and 400 K, under different 2.1 Synthesis The polycrystalline new solid solutions applied fields (500 Oe for zero-field-cooled/field-cooled Cu2MnxFe1ÀxSnS4 and the end members Cu2MnSnS4 and (ZFC/FC) cycles, and 10 kOe for measurements above TC. Cu2FeSnS4 were prepared by direct combination of powders Magnetization loops M(H) between þ50 and À50 kOe were of the corresponding high purity elements (99.99% Aldrich). measured at 2 K. The reaction mixture was sealed in evacuated quartz ampoules, manipulated under Ar atmosphere and heated 3 Results and discussion to 850 8C for about 72 h in a programmable furnace; then, 3.1 Chemical and thermal analysis In order to the reaction mixture was cooled by quenching in liquid check the purity of the investigated materials, SEM-EDS Table 1 Chemical composition analysis (% mass) of Cu2MnxFe(1Àx)SnS4 solid solutions. Cu Mn Fe Sn S estimated nominal 29.1 0 12.9 28.4 29.6 Cu1.98Fe1.00Sn1.03S3.99 Cu2FeSnS4 29.4 2.5 10.5 27.3 30.0 Cu2.01Mn0.20Fe0.82Sn1.00S3.99 Cu2Mn0.2Fe0.8SnS4 29.7 4.8 8.1 27.9 29.5 Cu1.99Mn0.37Fe0.62Sn1.00S3.91 Cu2Mn0.4Fe0.6SnS4 29.9 7.6 5.3 27.3 29.7 Cu2.05Mn0.60Fe0.41Sn1.00S4.03 Cu2Mn0.6Fe0.4SnS4 29.3 10.5 2.4 27.8 30.0 Cu1.97Mn0.82Fe0.18Sn1.00S4.00 Cu2Mn0.8Fe0.2SnS4 30.2 13.5 0 26.8 29.5 Cu2.10Mn1.09Sn1.00S4.07 Cu2MnSnS4 www.pss-b.com ß 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim b solidi p status s s physica 960 F. López-Vergara et al.: Magnetic properties and crystal structure of Cu2MnxFe1ÀxSnS4 analyses performed in powder samples revealed that the chemical compositions were uniform throughout the scanned region and correspond fairly well to the nominal ones. The samples were found to be homogeneous within the analytical uncertainty. The chemical data are given in Table 1. The DTA–TGA heating/cooling was conducted in argon atmosphere. The studied solid solutions behave similarly and they are stable up to aprox. 400 8C. After this temperature, they begin to decompose, a process, which occurs in two stages. The first stage of decomposition can be attributed to the partial sulfur loss. In a second stage, at 750 8C, the phases decompose totally to metal sulfides, which were identified by XRD analysis of the residues. 3.2 X-ray diffraction results In order to clarify the crystal structure of the solid solutions Cu2MnxFe1ÀxSnS4,a structural study by single-crystal X-ray diffraction was performed.

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