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Ni 1 − x TixMnSb polycrystalline alloys in the range 0 ≤ x ≤ 0. 2 0 were synthesized employing the standard solid-phase synthesis method. The crystal, magnetic, as well as electrical properties of the alloys were investigated using neutron powder diffraction and magneto-resistance measurements. The results reveal that the substitution of Ti for Ni within the temperature range of 2.5–300 K does not induce alterations in the crystal and magnetic structures of NiMnSb. The ordered Ni magnetic moment approaches zero. The study of the electrical transport properties of the Ni 1 − x TixMnSb alloys, where 0 ≤ x ≤ 0. 2 0 , has demonstrated a half-metallic state at low temperatures and metallic conductivity for temperatures exceeding 160 K. A semiconductor state manifests at titanium concentrations of x = 0.2 and was observed at temperatures below 21 K. The obtained experimental results are elucidated through first-principles theoretical calculations. [ABSTRACT FROM AUTHOR]

Impacts of hydrogen annealing on crystallographic characterization, electronic structure, and optical, photocatalytic, and magnetic properties of polycrystalline Zn1−xCoxO (x = 0.01–0.06) samples have been considered. Structural analyses based on powder X-ray diffraction, Rietveld refinement, and Raman spectroscopy prove all materials having the P63mc wurtzite-type structure. The Co-doping and hydrogenation changed the concentration of Zn– and O–related defects whose energy levels occupy the band gap. This also enhanced photocatalytic performance of hydrogenated samples with x > 0.02. X-ray and UV–Vis absorption analyses indicate the substitution of Co2+ for Zn2+ in the wurtzite-type ZnO lattice, leading to irregularly changed the unit-cell parameters. While all the as-prepared samples are paramagnetic, the hydrogenated ones exhibit weak ferromagnetism. Ferromagnetic (FM) ordering increases when x increases, particularly for x ≥ 0.02. According to the results achieved from studying crystalline and electronic structures, we believe that oxygen-vacancies-mediated interactions between Co2+ ions and H–Co–H exchange dimers enhanced FM ordering in hydrogenated Zn1−xCoxO. Computational investigations have also indicated that the magnetization value of H–Zn1−xCoxO is influenced by the positioning of the H dopant, meaning that the couplings between Co and H play an essential role in establishing FM order in H–Zn1−xCoxO. [ABSTRACT FROM AUTHOR]

The pressure-driven phase transformation in polycrystalline BaTi 1 − x FexO3 (x = 1 %), synthesized by a solid-state reaction method, was investigated using synchrotron X-ray diffraction and Raman spectroscopy. All measurements were performed at room temperature within a large pressure range up to 36.5 GPa. The results clearly demonstrate a phase transformation from the ferroelectric tetragonal structure of P4mm symmetry to the paraelectric cubic structure of Pm-3m symmetry in the studied sample at the pressure of about 18 GPa. This phase transformation pressure is much higher than those previously reported for BaTiO3-based systems, indicating the stabilization of the ferroelectric phase by doping 1% Fe into BaTiO3. Feature modes of the tetragonal phase still persist while some new modes appear in the Raman spectra at pressures above 18 GPa. This is probably due to accumulated stress and/or local microscopic disorders in the sample, which are associated with the displacement of the Ti atoms along unit-cell diagonals. [ABSTRACT FROM AUTHOR]

We have investigated the hydrogen-annealing influence on the crystalline and electronic structures, and magnetic properties of La2/3Ca1/3MnO3 (LCMO). The results have indicated that the annealing at 700 and 900°C (labeled as LCMO-700 and LCMO-900, respectively) readily reduced single-phase LCMO, resulting in a complex phase composition of several isostructural oxygen-deficient perovskite-type phases coexisting with the Ruddlesden-Popper (La/Ca)2MnO4-type phase. While a Mn3+/Mn4+ mixed valence is present in LCMO, the hydrogenannealed samples mainly have Mn2+ and Mn3+ ions. Under such circumstance, large changes in magnetic parameters have been recorded, such as remarkable decreases in values of the magnetization, the Curie temperature (from 251 K for the as-prepared LCMO through 240 K for LCMO700 to ³221 K for LCMO-900), and the magnetic-entropy change. Particularly, the crystal and electronic-structure changes also enhance the magnetic inhomogeneity, resulting in a strong development of the Griffiths phase, and cause the first-to-second-order phase transformation. These results reflect the instability of the LCMO perovskite-type manganite versus hydrogenation. [ABSTRACT FROM AUTHOR]