We present here, the results of an investigation on giant magnetoimpedance (GMI) effect in both annealed and as‐quenched Co70Fe5Si15B10 and Co70Fe5Si15Nb2.2Cu0.8B7 ribbons. Substitution of Cu and Nb for B in an initial Co70Fe5Si15B10 composition forming the Co70Fe5Si15Nb2.2Cu0.8B7 composition improves both GMI effect and its field sensitivity. The GMI effect was more pronounced in the annealed samples. The field sensitivity of both the longitudinal permeability ratio and the magnetoimpedance ratio for the annealed Co70Fe5Si15Nb2.2Cu0.8B7 ribbon increase exponentially as the testing temperature is increased, indicating that the magnetic permeability is very sensitive to the temperature. The results obtained are of significant importance in developing quick‐response magnetic sensors. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

PACS 75.30. Sg, 75.47.Lx Magnetic entropy change in and above the room-temperature region has been measured for La 0.7 Sr 0.3 Mn 1-x M x O 3 (M = Al, Ti) by means of magnetization measurements in magnetic fields up to 6 T. The magnetocaloric effect (MCE) becomes strongest at the Curie temperature T c that is tuned to ~300 K by the substitution of Al or Ti for Mn. While the substitution of Al for Mn drastically reduces the entropy change, it extends considerably the working temperature span and improves the relative cooling power (RCP). The MCE and RCP seem to be only lightly affected by Ti substitution. Although manganites are considered potential for magnetic refrigerants, the limitations for achieving strong MCE in the materials are also discussed.

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A hydrothermal method was used to prepare three nano-crystalline samples of TiO2 (S1), N-doped TiO2 (S2), and (N, Ta)-codoped TiO2 (S3) with average crystallite sizes (D) of 13–25 nm. X-ray diffraction studies confirmed a single phase of the samples with a tetragonal/anatase structure. A slight increase in the lattice parameters was observed when N and/or Ta dopants were doped into the TiO2 host lattice. Detailed analyses of extended X-ray absorption spectra indicated that N- and/or Ta-doping into TiO2 nanoparticles influenced the co-ordination number and radial distance (R) of Ti ions in the anatase structure. Concerning their absorption spectra, (N, Ta)-doping narrowed the band gap (Eg) of TiO2 from 3.03 eV for S1 through 2.94 eV for S2 to 2.85 eV for S3. Such results revealed the applicability of these nanoparticles in the photocatalytic field working in the ultraviolet (UV)-visible region. Among these, photocatalytic activity of S3 was the strongest. By using S3 as a catalyst powder, the degradation efficiency of methylene blue solution was about 99% and 93% after irradiation of UV-visible light for 75 min and visible-light for 180 min, respectively.

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