Synthesis, structure and magnetic properties of R–W–O–N (R=Nd and Eu) oxynitrides
| Autor: | J. Isasi-Marín, R. Pastrana-Fábregas, Concepción Cascales, Regino Sáez-Puche |
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| Rok vydání: | 2007 |
| Předmět: |
Magnetic moment
chemistry.chemical_element Condensed Matter Physics Magnetic susceptibility Electronic Optical and Magnetic Materials Inorganic Chemistry Tetragonal crystal system Paramagnetism Crystallography Nuclear magnetic resonance chemistry Ferrimagnetism Materials Chemistry Ceramics and Composites Physical and Theoretical Chemistry Europium Saturation (magnetic) Powder diffraction |
| Zdroj: | Journal of Solid State Chemistry. 180:92-97 |
| ISSN: | 0022-4596 |
| DOI: | 10.1016/j.jssc.2006.09.025 |
| Popis: | Neodymium and europium tungsten oxynitrides have been synthesized by the nitridation of corresponding R 2 W 2 O 9 precursor oxides, in ammonia flow at 1173 K during 24 h. The obtained polycrystalline neodymium oxynitride phase, with NdWO 3.05 N 0.95 composition, crystallizes with the tetragonal symmetry of the scheelite-type structure, space group S.G. I 4 1 / a (#88). The analogous europium derivative, with formula EuWO 1.58 N 1.42 , presents the cubic perovskite-type structure, S.G. Pm 3 ¯ m (# 221). Unit-cell parameters, a =5.255(1) A, c =11.399(3) A, and a =3.976(3) A, have been established from Rietveld refinements of collected X-ray powder diffraction patterns for the Nd and Eu- oxynitrides, respectively. Magnetic susceptibility measurements show that NdWO 3.05 N 0.95 behaves as paramagnetic in a wide range of temperature T ∼50–300 K. The downwards deviation from the Curie–Weiss law below 40 K reflects the splitting of the 4 I 9/2 ground state of Nd 3+ experienced under the influence of a S 4 crystal field CF potential, as the successful reproduction of the magnetic susceptibility χ −1 m vs. T , using semi-empirical structure-derived CF parameters, indicates. EuWO 1.58 N 1.42 is paramagnetic down to 20 K, and the measured effective magnetic moment 8.01 μ B is indicative of the presence of Eu 2+ in this oxynitride. The observed sudden jump in the magnetic susceptibility at 20 K and the value of 6 μ B for the saturation moment is attributed to the onset of ferrimagnetic interactions in which the Eu 2+ and W 5+ sublattices appear to be involved. |
| Databáze: | OpenAIRE |
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