[Fe₃(hyetrz)₆(H₂O)₆](CF₃SO₃)₆ (where hyetrz = 4-(2'-hydroxyethyl)-1,2,4-triazole) is an interesting linear, trinuclear iron(II) compound with incomplete spin crossover. We reinvestigated crystal structure of this compound in the wide temperature range because the knowledge only about the crystal structure in the initial and final phases is not sufficient to establish correlations between the structural and magnetic properties of the spin crossover system. The complex [Zn₃(hyetrz)₆(H₂O)₆](CF₃SO₃)₆ was used for comparison because it does not exhibit spin crossover phenomenon and it is isostructural with a high spin phase of Fe(II).
Single crystals of ZnCr_{2}Se_{4} spinel doped with vanadium were prepared by chemical vapour transport. The chemical compositions of three crystals have been determined by X-ray diffraction. The structure refinement using the SHELXL-93 program system determine the cation distribution in the system as ZnCr_{2-x}V_{x}Se_{4}. For x values equal to 0.03, 0.1 and 0.13 the observed symmetry was cubic, space group Fd3m. Based on the structural data, influence of the V ions on the magnetic and electrical properties has been analyzed.
Measurements of the magnetic properties, the electrical conductivity and the Seebeck effect were performed on single crystals (Cd_{x}Al_{y})[Cr_2]Se_{z} between 77 and 300 K. All samples have a ferromagnetic order with the Curie temperature of 130 K and the paramagnetic Curie-Weiss temperature of 155 K. Both these temperatures do not depend significantly on the Al substitution. The electrical conductivity of single crystals CdCr_2Se_4 doped with Al was p-type and showed the change of log σ versus 1/T slope above 150 K. This fact is interpreted as being due to the onset of impurity conduction and structural defects.
Pure and undoped strontium-barium niobate Sr_{0.40}Ba_{0.60}Nb₂O₆ (SBN40) single crystals grown by the Czochralski method were investigated by single crystal X-ray diffraction methods. The study below T_{C} (429 K for SBN40) confirmed the structure with P4bm space group. Above this temperature the structure transforms into the paraelectric, centrosymmetric one with P4/mbm space group. Analysis of the recorded diffraction patterns allowed to observe several signs of crystal structure modulation. On the registered diffraction images satellite reflections were found. A modulation vector q=(δ,±δ,), where δ=0.3075(6) (at room temperature) was found and it was similar to that occurring in the SBN61. In addition, above the phase transition temperature on the (hk) planes with l integer a weak diffuse scattering was observed.
Both (NbSe₄)₃I and (NbSe₄)_{10/3}I compounds are interesting system possessing quasi one-dimensional linear chain character and exhibiting nonlinear transport properties with a second order phase transition. The compounds are built of NbSe₄ antiprisms, stacked along the tetragonal c axis into chains in a screw-like arrangement. Performed X-ray low temperature single crystal diffraction measurements allowed to solve, refine and analyze crystal structures of both compounds at 14 K. While (NbSe₄)_{10/3}I compound undergoes structural phase transition to monoclinic phase, (NbSe₄)₃I remains in tetragonal symmetry. Iodine atoms are responsible for the differences in (NbSe₄)_{10/3}I and (NbSe₄)₃I structures causing different spacing in the infinite NbSe₄ chains.
Y_{3}Al_{5}O_{12} (YAG) single crystals doped with vanadium ions (V^{3+}) were obtained by the Czochralski method. The X-ray photoelectron spectra of YAG:V annealed in reducing atmospheres: H_{2}, vacuum and H_{2} + vacuum are presented and compared with the spectra of the YAG ceramics. The X-ray photoelectron spectra showed that the vanadium dopant concentration in YAG:V crystals is lower than a nominal one. For the "as grown" YAG:2.8at.%V crystal vanadium exists in the mixed valence state. The increase in lattice parameters for the samples annealed in hydrogen was found.
The influence of the external magnetic field on magnetic and crystallographic structure of magnetite was studied. We have confirmed, by means of vibrating sample magnetometer measurements, that external magnetic field can switch the easy magnetic axis to the new crystallographic direction. We have also proved by the direct observation of the crystalline structure that this phenomenon is strictly related to the crystallographic structure relaxation.