2,089 publications from this institution
HCHO, CH3CHO and (CH3)2CO are shown to adsorb molecularly on a clean Cu(110) surface at 80 K and transform to different surface species on increasing the temperature. On a Cu(110) surface modified with aluminum, adsorption of HCHO, CH3CHO and (CH3)2CO is dissociative. The two aldehydes undergo chemical transformations on a Cu(110) surface covered with atomic oxygen.
We have studied the resistivity (ϱ) and the magnetoresistance (MR) in sintered samples of La 1−x Ca x MnO 3 for 0.1 ≤ x ≤ 0.9 in the temperature range 4.2K ≤ T ≤ 400K in magnetic fields H ≤ 6T. We have observed giant negative magnetoresistance in the whole composition range, although the magnitude of MR depends on the level of doping, the peak in the magnitude of MR [ (ϱ(H) − ϱ(0)) ϱ(0) ] at 6T being be as high as 90%. The magnitude of the MR generally increases as the temperature corresponding to the MR peak decreases. All the samples with x ≤ 0.5 show a ferromagnetic transition with the temperature dependence of ϱ showing a metallic behavior ( dϱ dT > 0) below the Curie temperature. The sample with x = 0.9 shows insulating behavior over the entire temperature range but the MR shows a peak at low temperatures.
Hybrid organic–inorganic framework compounds constitute an important class of materials whose properties, especially paired ones, have not been adequately investigated hitherto. In this communication, we report the non-linear optical properties of hybrid compounds exhibiting interesting magnetic properties.
By the employment of hydrothermal methods, four lead 1,3-cyclohexanedicarboxylates with the compositions Pb(1,3-CHDC)(H(2)O), I, [(OPb(4))(2)(OH)(2)(C(2)O(4))(1,3-CHDC)(4)].H(2)O, II, Pb(2)(1,3-CHDC)(2)(H(2)O), III, and (OPb(3))(1,3-CHDC)(2), IV, have been prepared and characterized. Of these, I and II have layered structures while III and IV have three-dimensional structures. I-III are hybrid structures possessing extended inorganic connectivity in one or two-dimensions (I(n), n = 1 or 2) involving infinite Pb-O-Pb linkages along with zero or one-dimensional organic connectivity (O(m), m = 0 or 1). I contains two types of layers with different connectivities (I(1)O(1) and I(2)O(0). III is a truly 3-D hybrid compound with I(2)O(1) type connectivity. IV has three-dimensional organic connectivity (O(3)) but no inorganic connectivity (I(0)). The conformation of the CHDC anion is e,e in I-III and a,e in IV. In all these compounds, the lead atom has hemi- or holodirected coordination geometry.
Films of charge-ordered ${\mathrm{Nd}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3},$ ${\mathrm{Gd}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3},$ ${\mathrm{Y}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3},$ and ${\mathrm{Nd}}_{0.5}{\mathrm{Sr}}_{0.5}{\mathrm{MnO}}_{3}$ show insulator-metal transitions on the passage of small electrical currents. That such an electric-field-induced transition occurs even in ${\mathrm{Y}}_{0.5}{\mathrm{Ca}}_{0.5}{\mathrm{MnO}}_{3}$ where the charge-ordered state is not affected by magnetic fields is noteworthy. The transition is attributed to the depinning of the randomly pinned charge solid. These materials also exhibit an interesting memory effect probably due to the randomness of the strength as well as the position of the pinning centers.
No abstract is provided for this article.
Review: (55 refs.
When I was very young, I remember people doing balloon experiments in the Indian Institute of Science campus, Bangalore. It was young Sarabhai with Homi Bhabha carrying out cosmic ray experiments. Vikram Sarabhai officially had registered for the Ph D degree of Cambridge University under the supervision of C. V. Raman, but his immediate guide was Homi Bhabha. Though I could not have known him at that time, I got in touch with him in 1961 when he was the President of the Physics Section of the Indian Science Congress. He had invited me to give a talk on Spectroscopy in Chemistry. After that meeting, we became good friends and met each other on different occasions.
Small exothermic reaction peaks are observed in the differential thermal curves of carbonates. The heat evolution is probably due to the removal of internal crystal defects in the metastable oxide lattices.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
