6 research outputs found
Superconductivity of MI(MII0.5, Si0.5)2 (MI=Sr and Ba, MII=Al and Ga), ternary silicides with the AlB2-type structure
Ternary silicides MI(MII0.5, Si0.5)2 (MI=Sr and Ba, MII=Al and Ga) were
prepared by Ar arc melting. Powder X-ray diffraction indicates that they have
the AlB2-type structure, in which Si and MII atoms are arranged in honeycomb
layers and MI atoms are intercalated between them. Electrical resistivity and
dc magnetization measurements revealed that Sr(Al0.5, Si0.5)2 is
superconductive, with a critical temperature for superconductivity (TC) of 4.2
K, while Ba(Al0.5, Si0.5)2 is not at temperatures ranging above 2.0 K.
Sr(Ga0.5, Si0.5)2 and Ba(Ga0.5, Si0.5)2 are also superconductors, with TCs of
5.1 and 3.3 K, respectively.Comment: 5 pages, 3 tables, 4 figure
Ab initio calculation of resonant X-ray scattering in Manganites
We study the origin of the resonant x-ray signal in manganites and generalize
the resonant cross-section to the band structure framework. With {\it ab
initio} LSDA and LSDA+U calculations we determine the resonant x-ray spectrum
of LaMnO. The calculated spectrum and azimuthal angle dependence at the Mn
-edge reproduce the measured data without adjustable parameters. The
intensity of this signal is directly related to the orthorhombicity of the
lattice. We also predict a resonant x-ray signal at the La -edge, caused by
the tilting of the MnO octahedra. This shows that the resonant x-ray signal
in the hard x-ray regime can be understood in terms of the band structure of a
material and is sensitive to the fine details of crystal structure.Comment: 4 pages, 4 figures, accepted for publication in Phys. Rev.