Co-occurrence of superparamagnetism and anomalous hall effect in highly reduced cobalt-doped rutile TiO2-delta films

We report a detailed magnetic and structural analysis of highly reduced Co doped rutile TiO(2-delta) films displaying an anomalous Hall effect (AHE). The temperature and field dependence of magnetization, and transmission electron microscopy, clearly establish the presence of nanosized superparamagnetic cobalt clusters of approximately 8-10 nm size in the films at the interface. The co-occurrence of superparamagnetism and AHE raises questions regarding the use of the AHE as a test of the intrinsic nature of ferromagnetism in diluted magnetic semiconductors.     

Single crystal EPR study of VO(II)-doped magnesium

Single crystal EPR studies of VO(II)-doped magnesium potassium Tutton's salt have been carried out at room temperature. The results indicate that the paramagnetic impurity has entered the lattice, both substitutionally and interstitially and the maximum hyperfine for the substitutional site along the a axis corresponds to the minimum hyperfine for interstitial site and vice versa. The spin Hamiltonian parameters obtained from single crystal data for these sites are: Site 1, gparallel = 1.954(1); gperpendicular = 1.998(1), Aparallel = 19.80(2) mT; Aperpendicular = 7.61(2) mT; Site 2, gparallel = 1.997(1); gperpendicular = 1.952(1), Aparallel = 7.66(2) mT; Aperpendicular = 19.85(2) mT. Superhyperfine from ligand protons have been observed at certain orientations for Site 2 impurity. Powder spectrum shows a set of eight parallel and perpendicular features indicating the presence of only one site and these values matched with Site 1 values. From these observations, it has been concluded that the two vanadyl impurities are approximately at right angles to each other. Cooling the sample to 77 K does not change the spectra appreciably. The admixture coefficients have been calculated from Site 1 data, which agree well with the reported values.     

Axisymmetric non-linear oscillations of isotropic layered circular plates

Non-linear equations of motion for isotropic layered circular plates are presented for axisymmetric motion. Further simplification is made by ignoring the in-plane and rotatory inertia terms. Explicit solutions are obtained for the forced and free oscillations. In this case it is found that the non-linearity is of hardening type. Numerical results are presented for the case of a two layered plate of aluminium and steel.     

Stereochemistry of benzophenone derivatives: crystal and molecular structure of 3,3′-dibromobenzophenone

The structure of 3,3′-dibromobenzophenone has been reinvestigated using new three-dimensional data. Crystals of 3,3′-dibromobenzophenone are orthorhombic:a = 4·05,b = 11·74,c = 24·80 Å,Z = 4, space groupPbcn. The structure has been refined by three-dimensional methods, including anisotropic full-matrix least squares, to anR index 0·104. The conformation of isolated molecules of benzophenone,pp′-dimethoxy benzophenone and 3,3′-dibromobenzophenone have been calculated by semi-empirical methods, and the results are compared with those obtained from X-ray crystallographic investigations on these compounds. It has been found that the calculated geometries of isolated molecules of benzophenone and its derivatives are different from those observed in the crystal structures of these compounds.