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In this study we investigated the influence of Gd 3 + ions on the structural and magnetic properties of (Nb + Al) co-doped TiO 2 single crystals with nominal composition Ti 0.995 (Nb 0.667 Al 0.333) 0.005 O 2 (TNA) and Ti 0.995 (Nb 0.667 (Al 0.1665 Gd 0.1665)) 0.005 O 2 (TNAGd) grown in an optical traveling floating zone (TFZ) furnace. The crystal structure and phase purity investigated by X-ray diffraction (XRD) and High resolution transmission electron microscopy (HRTEM) images of selected area electron diffraction (SAED) patterns confirmed the rutile crystal nature for both TNA and TNAGd samples. The magnetic properties were studied from 3 to 400 K in magnetic fields up to 60 kOe. ZFC/FC curves revealed paramagnetic behavior for TNA sample, while the presence of Gd 3 + ions in the crystal structure drastically affected the magnetic properties turning to ferromagnetic behavior. The isothermal magnetization, M(H) curves for TNAGd samples were analyzed by the bound magnetic polaron (BMP) model. At the lowest temperature the values of the total moment of BMP's (M 0), spontaneous moment of a single BMP (m s), and the concentration of BMP's (N) were found to be 1.58 emu / cm 3 , 840 μ B , and 3.2 × 10 19 BMP / cm 3 , respectively. The number of Gd 3 + ions per BMP was ~ 113 and 75% of Gd 3 + ions were inside the BMP's and the remaining 25% were outside but diluted in the matrix or interacting antiferromagnetically. [ABSTRACT FROM AUTHOR]

In this work, structural and physical properties are revisited in the MoO 2 compound. MoO 2 single crystals have been prepared by chemical vapor transport technique and characterized by X-ray diffraction, neutron diffraction, high-resolution thermal expansion, electrical resistance measurements, and heat capacity. Electrical resistivity, heat capacity, and thermal expansion measurements show two clear features which are related to phase transitions on the MoO 2 compound. These results suggest that an electronic-type transition occurs near 220 K and a structural transition at ∼267 K. [ABSTRACT FROM AUTHOR]