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New solid solutions Cu 2 Mn x Fe 1Àx SnS 4 were prepared by direct combination of the corresponding elements at 850 8C. The crystal structure of Cu 2 Mn 0.4 Fe 0.6 SnS 4 was determined by single-crystal X-ray diffraction. This phase is described in the space group I 42m where each cation is tetrahedrally coordinated to four sulfur anions in a sphalerite-like arrangement. The XRD patterns of the solid solutions Cu 2 Mn x-Fe 1Àx SnS 4 were fully indexed in the space group I 42m 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 with AF interactions, weaker by more than one order of magnitude compared to other diluted magnetic semiconductors (DMSs) with zinc-blende or wurzite crystal structure.

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The crystalline structure of spinels is extremely flexible due to the presence of several sublattices in which the cations can be distributed and localized in different crystallographic sites depending on their sizes, oxidation states or coordination numbers. Cationic substitution and ions-extraction are appropriate tools to change the oxidation state inside the spinel structure, thus substantially modifying the magnetic properties. The spinel sulfide CuCr 2 S 4 is a metallic ferromagnet with T C = 377 K, where Cr is mixed-valence Cr

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Polycrystalline Cu 2 ZnSnS 4-X Se X (X=1, 2, 3) compounds were synthesized by conventional solid-state reactions. The samples were characterized by powder X-ray diffraction (XRD), energy-dispersive X-ray analysis (SEM-EDS), Raman spectroscopy, diffuse reflectance UV-vis and Photoluminescence. All of phases crystallize in the tetragonal kesterite-type structure. The powder X-ray diffraction (XRD) patterns were indexed in the space group . No secondary phases were detected in XRD patterns. The results from diffuse reflectance show band gap between 1.26 -1.17 eV, when S is gradually replaced by Se. The PL spectrum of Cu 2 ZnSnS 4-x Se x phases shows nearly symmetrical band, which shifted linearly to the lower energy with increasing Se content. The selenized (CZTSSe) phases are promising candidates to be used as absorbing material in solar cells

The solid solutions Cu 2 Fe 1-X Co X SnS 4 , with stannite-type structure are stable up to about 800ºC. The electrical properties of the Cu 2 Fe 0.4 Co 0.6 SnS 4 ceramic were investigated by complex impedance. The real and imaginary dielectric permittivity dependence with the temperature were measured between 10kHz and 1 MHz in temperature range 77-280K, finding that the ceramic present the characteristics behavior of a dielectric relaxation between 100 and 250 K, with a maximum at approximately 200 K. The electric permittivity found has orders of magnitude between 10 2 and 10 3 . A space charge polarization mechanism is suggested to explain the observed electric relaxation.