Flux growth and characterization of Sr 2 NiWO 6 single crystals C.G.F. Blum a , A. Holcombe b , M. Gellesch a , M.I. Sturza a , S. Rodan a , R. Morrow c , A. Maljuk a , P. Woodward c , P. Morris b , A.U.B. Wolter a , B. Büchner a,d , S. Wurmehl a,d,n a Leibniz Institute for Solid State and Materials Research Dresden IFW, Institute for Solid State Research, 01069 Dresden, Germany b Department of Materials Science and Engineering, The Ohio State University, Columbus, OH 43210, USA c Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210, USA d Institute for Solid State Physics, TU Dresden, 01062 Dresden, Germany article info Article history: Received 17 November 2014 Received in revised form 25 February 2015 Accepted 6 April 2015 Communicated by A.G. Ostrogorsky Available online 15 April 2015 Keywords: A1. Characterization A1. Crystal structure A2. Growth from solutions A2. Single crystal growth B2. Perovskites B2. Magnetic materials abstract Single crystals of the double perovskite Sr 2 NiWO 6 were synthesized via SrCl 2 flux growth using high quality, phase-pure polycrystalline Sr 2 NiWO 6 as precursor material. This high quality precursor enabled us to grow large and phase pure crystals with sizes up to 1 mm  1 mm in the basal plane and octahedral morphology. We measured the temperature dependence of the magnetization along the c-axis and along the ab plane. The analysis of the data allows a precise determination of the effective magnetic moment and the Curie–Weiss temperature. Sr 2 NiWO 6 orders antiferromagnetically at T N ¼54 K as revealed by magnetization and specific heat data. & 2015 Published by Elsevier B.V. 1. Introduction The A 2 BB 0 O 6 double perovskites are among the most interesting classes of transition metal oxides and are typically mentioned in the context of magnetic materials with peculiar properties such as colossal magneto-resistance and half-metallic ferromagnetism. Sr 2 FeMoO 6 ren- ders the best studied member of this class of materials as it is the paradigm of an oxidic, metallic ferromagnet with expected 100% spin polarization [1–4]. Typically, the magnetic properties of double per- ovskites are governed by long-range superexchange (SE) interactions; in the speci fic case of Sr 2 NiWO 6 , the SE interactions take place along Ni 2þ –O 2 –W 6þ –O 2 –Ni 2þ chains [5]. Interestingly, the temperature of the antiferromagnetic transition (T N ¼ 54 K) is rather high taking into account the long distance of the SE interaction path. So far, no single phase polycrystals of Sr 2 NiWO 6 are reported to be synthesized by standard solid state reaction and typically both SrWO 4 and Sr 2 WO 5 are found as secondary phases (compare e.g. [6–8]). So far, only a sol–gel preparation route was employed to yield single phase polycrystals [7]. One publication reports on successful crystal growth for Sr 2 NiWO 6 , however, yielding very small crystals [9]. The magnetic signal of individual crystals was too low to be resolved and magnetic properties had to be measured using a mixture of powders of several crystals, without possibility of inves- tigation of the anisotropic properties of Sr 2 NiWO 6 . In this work, we report on the growth of Sr 2 NiWO 6 single crystals by the flux method using anhydrous SrCl 2 as flux. The starting material for the growth was high quality, single phase polycrystalline Sr 2 NiWO 6 . The resulting crystals were characterized regarding their composition, structure, thermodynamic and magnetic properties. 2. Experimental details 2.1. Preparation of precursor materials We used the following solid-state technique to synthesize single phase polycrystalline Sr 2 NiWO 6 : we synthesized NiWO 4 as precursor. Accordingly, stoichiometric amounts of NiO (green, 78.5% Ni, Alfa Aesar) and WO 3 (99.8%, Alfa Aesar) were carefully ground and the homogeneous mixture of NiO and WO 3 was heated to 1000 1C for 10 h in air, as described by Zhou et al. [10]. Stoichiometric amounts of SrCO 3 ( r99:9%, Sigma-Aldrich) were then added to the NiWO 4 , ground and heated to 1400 1C for 8 h in air to complete the synthesis. This higher reaction temperature, reported by Iwanaga et al. [11], was used to achieve single phase material. This precursor technique differs from other traditional solid-state techniques reported in the literature [11,6] Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jcrysgro Journal of Crystal Growth http://dx.doi.org/10.1016/j.jcrysgro.2015.04.004 0022-0248/& 2015 Published by Elsevier B.V. n Corresponding author. E-mail address: s.wurmehl@ifw-dresden.de (S. Wurmehl). Journal of Crystal Growth 421 (2015) 39–44