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Tin (IV) disulfides (SnS 2 ) doped with Fe ions are prepared through the molten salt solid state reaction at 280 °C and the effect of the Fe-doping on their structural and optical properties is reported. They were found to be nanocrystalline hexagonal structure with nanoflakes morphology with an average size 30 nm. The analysis of the optical data showed that all the samples are indirect semiconductors. Two absorption bands are observed in their optical diffuse reflectance spectra which indicate setting of two photons absorption processes due to formation of Fe intermediate band. The band gaps E g H I n d and E g L I n d that correspond to the two photons absorptions are found to vary from 1.49 to 1.09 eV and 0.76 to 0.93 eV, respectively. The most significant findings is that the sum of E g H I n d and E g L I n d has values between 2.25 and 2.02 eV which reproduces or slightly enhances the band gap value of the parent SnS 2 (2.01 eV). This finding is directly related with the perseveration of the output voltage ( V o ) which is a major condition required for realization of intermediate band solar cells with high solar conversion efficiency. [ABSTRACT FROM AUTHOR]

Abstract: Successful preparation of double perovskite oxides of chemical formula ALaFeTiO6 (A=Ba, Sr and Ca) has been achieved by following the precursor method. The samples were studied by means of X-ray diffraction and Mössbauer spectroscopy. The Rietveld analysis of the X-ray diffraction data showed that all the samples have anti-site disorder. The presence of anti-site disorder has altered the electronic environment around the Fe ion sites which creates electric field gradient between two different sites. Observation of quadruple splitting in the ideal cubic perovskite BaLaFeTiO6 (its tolerance factor equals 1) is the evidence of this anti-site generated electric field gradient. The valence state of the Fe atom determined from the measurements of the Mössbauer effect of 57Fe at room temperature and 80K showed that the iron ion has the Fe3+ high spin state as extracted from the values of the isomer shift for all the samples. It is evidenced that the anti-site disorder has no appreciable effect on the spin state of the Fe ion, but alters the charge densities at the Fe sites and influences the hyperfine parameters of the present samples. Weak ferromagnetism is observed in CaLaFeTiO6 and SrLaFeTiO6 and is related to both the internal pressure and the anti-site effect which facilitate the occurrence of the antiferromagnetic interaction with canted spin. [Copyright &y& Elsevier]

Abstract: The electronic structure and magnetic properties of pseudo-cubic and tetragonal double perovskite oxides Sr2MnNbO6, Sr2FeMoO6 and Sr2NiRuO6, have been determined by using the full potential linear augmented plane wave method (FP-LAPW) employing the LSDA+U scheme. The spin–orbit coupling (SOC) has been taken into consideration. These calculations showed that all the three compounds in their two crystalline structures are half metallic. The values of the total energy have indicated that first two compounds prefer the tetragonal structures while the third one prefers the pseudo-cubic structure. The obtained magnetic moments indicate that Sr2MnNbO6 and Sr2NiRuO6 are ferromagnetic while Sr2FeMoO6 has ferrimagnetic ordering. The effect of the spin–orbit coupling was seen to grow from quenched to weakly unquenched to unquenched as going from Nb to Ru and from Mn to Ni as signified by the values of the orbital magnetic moments of the 3d and 4d orbitals. Sr2NiRuO6 shows half-metallic conduction and ferromagnetism in accordance with the superexchange interaction of Goodenough–Kanamori–Anderson (GKA). [ABSTRACT FROM AUTHOR]

Abstract: The paramagnetic susceptibility measured on La1−x Y x Sr2−y Ca y Mn2O7 (x, y or z=0, 0.03 and 0.1) manganites does not obey the Curie–Weiss law. The Curie constant exceeds the expected values by more than order of magnitude. Based on strong disorder we have compared the experimental data with predictions based on Griffith''s singularity model. We find that this model allows for consistent interpretation of the data in contrary to a model assumes that magnetic polarons make contribution akin to cluster to susceptibility. In particular the values of Curie constant agree excellently with those theoretically expected, whereas the magnetic polarons model is less satisfactory. [Copyright &y& Elsevier]