Xia Yuan-Fu

An investigation of the structural effects of Fe3+ in the alkali-silicate glasses

Abstract The coordination states of Fe3+, B3+ and Al3+ ions in the alkali-silicate glasses have been determined. The structural effects of these cations coexisting in the glass, and the effects of the iron and boric oxide anomaly on glass density, are also analysed.

Mössbauer studies on iron in polybasic silicate glass

Abstract Mossbauer absorption spectroscopy was used to study the behaviour of iron in varying concentrations and different reducing conditions in SiO 2 Na 2 OAl 2 O 3 ZnO glass systems. The results indicate that, for the glasses studied, the ferrous and ferric cations are in both tetrahedral and octahedral coordination in the matrix. The ratio of the number of Fe 2+ ions in tetrahedral to the total number of Fe 2+ ions is approximately constant to 0.6, and this ratio, similar to Fe 3+ ions, is not composition-dependent. In addition, the line width is not affected by varying iron content and reducing condition of the glass. Ferric iron is prodominantly octahedrally coordinated when the iron concentration is low. The results of Mossbauer analysis above are also well consistent with the ones of wet chemical analysis, which is greatly different from some results studied before.

Mössbauer Investigation of the Ferromagnetic Coupling in Copper-Iron Polycyanides

One of the Prussian blue analogs, molecular magnet CuII3[FeIII(CN)6]211.6H2O, was investigated by Mossbauer spectroscopy. It was found that transition temperature was around TC = 18.5 K from paramagnetic phase to ferromagnetic phase. The β value of the critical exponent is around 0.338 at magnetic ordering temperature. Therefore, the ferromagnetic coupling interaction of Cu-Fe cyanide could be clearly explained by spin wave theory.

Magnetic Behaviour of Iron Oxychloride and Its Organometallic Intercalation Compounds Studied by Mössbauer Spectroscopy

Metallocene intercalate compounds with iron oxychloride, FeOCl(FeCp2)0.16 and FeOCl(CoCp2)0.36 with Cp being cyclopentadienyl group, are synthesized and characterized. Magnetism and the structure–property relations are investigated by magnetic measurement and 57Fe Mossbauer spectroscopy. The results show that the through-space dipolar interactions play a critical role in three-dimensional magnetic ordering of such layered compounds.

Synthesis and Magnetic Properties of the Intercalation Compound FePS3 (CoCp2)0.40

Intercalation compound FePS3 (CoCp2)0.40 (CoCp2 = cobaltocene) was synthesized, and the crystal structure and magnetic properties were studied by x-ray diffraction, magnetic susceptibility measurement, and Mossbauer spectroscopy. The crystal structure was indexed to monoclinic unit cell with a = 5.996 A, b = 10.106 A, c = 12.511 A, β = 105.916 degrees, and about 5.6 A expansion at the c-direction compared to pure FePS3. The Mossbauer spectra indicate that there are three kinds of divalent ions with high spin state in the intercalation compound, which implies charge transfer from guest to the Fe–S eg* anti-bonding orbits of the host lattice. No cationic vacancies are formed in the intercalation compound. The ferromagnetism at low temperature originates from the spin canting of divalent ions.

A M?ssbauer study of the magnetic coupling in iron phosphorous trisulfides

The polycrystalline sample of layered compound FePS3 has been investigated by using Mossbauer spectroscopy (12K to 300K), magnetic susceptibility measurements, x-ray diffraction and FTIR spectroscopy. The antiferromagnetic order exists below TN=120.5±1K. The Mossbauer spectra below TN indicate that the magnetization axis is perpendicular to the layer of {FePS}3 and the divalent iron cations are in their high spin configurations. By fitting the hyperfine field parameters near the Neel temperature, we obtain information on the nature of magnetic interactions in the material. The results show that the magnetic coupling can be treated by the two-dimensional Ising model and it can be interpreted on the basis of a crystal-field effect.

Influence of Residual Phases on the Behaviour of Gradual Spin Transition Complexes

In order to interpret the large shift between the observed high spin fraction and the so-called molar high spin fraction in the Mossbauer study on gradual spin transition complexes, we reveal numerically that the effects from residual phases in the substance should be considered in the correction by Debye-Waller factors. This result shows that similar Debye-Waller factors in high and low spin states agree well with the conclusion of experimental investigations for such gradual spin transition complexes.

Magnetic Properties and Mössbauer Spectroscopy for Complex Fe(tpa)(NCS)2

The studies of Mossbauer spectroscopy and magnetic properties for complex Fe(tpa)(NCS)2 exhibit that low spin → high spin (HS) transition may be thermally induced. The impurities such as HS-Fe2+ residue and HS-Fe3+, that were caused by compound preparation, play a significant role in the investigation of spin transition curve. The Mossbauer spectroscopy is used to observe the impurities as separated forms from the spin transition phase directly, and the magnetic susceptibility measurement is used to determine the total paramagnetism from all HS phases. With these two useful tools, an exact spin transition curve was defined by removing the magnetic contribution of the impurities.