A polarization Cu K-edge x-ray-absorption near-edge structure (XANES) study has been carried out on Pr2-xCexCuO4 single crystals. The spectra for x-ray polarization vector E nearly parallel to the crystal c axis suggest that electrons contributed by Ce doping are initially localized at the Cu site. The spectra for E perpendicular to the c axis exhibit an almost rigid edge shift to lower energies upon Ce doping. This suggests that the unoccupied in-plane Cu 4p states shift to lower energies. Therefore, the Ce doping donates electrons to the Cu site and also shifts the unoccupied 4p band. We propose that the upper unoccupied band consisting of predominantly Cu 3d states shifts downward and eventually joins the initially localized states near the Fermi level and thus, forms the conduction band in the n-type superconductor. © 1990 The American Physical Society.

The ternary compound YbRh1.4Sn4.6 with the phase I structure (simple cubic) when subjected to a pressure of 40 kbar at 800°C is found to transform to phase III structure (f.c.c.) with the composition YbRh1.1Sn3. The latter compound has a lattice parameter of a = 13.735 A ̊ which suggests that the Yb is in an intermediate valence state. The temperature dependence of magnetic susceptibility suggests that the Yb is in a homogeneously mixed valence state in the pressure synthesized product. In the phase I structure YbRh1.1Sn4.6 is superconducting at 8.6°K, but in the phase III structure the compound YbRh1.1Sn3 is not superconducting down to 0.9°K. It is suggested that superconductivity and mixed valence are incompatible. © 1981.

We have used high energy inelastic neutron scattering to study the magnetic fluctuation spectrum of La2CuO4 in the energy and momentum ranges 30≤h{stroke};σ≤140 meV and |q|≤0.2 Å-1, respectively. Our results are consistent, within the experimental error, with conventional spin wave theory the low temperature spin wave velocity, being 850±30 meV Å-1. © 1990.

We present data on the magnetic and superconducting properties of rare earth osmium stannides. The compounds of Tb and Ho are superconducting only, those of Er and Tm are reentrant superconductors, and those of Gd and Dy appear to exhibit some type of short range magnetic order at low temperatures. © 1982.

Inelastic light scattering studies of La2CuO4, both pure and doped with lead, over the energy range 01 have revealed the presence of high-frequency A1g scattering components, in the spectral region 35006000 cm-1, while also providing the complete line shape for the previously reported spin-pair mode of B1g symmetry. Two main bands, broad and overlapping, are observed in this region with maxima near 3500 and 5200 cm-1. The various spectral features show different resonance behavior. We suggest that a model based upon coupled spin and charge excitations will be required to describe these spectra. © 1989 The American Physical Society.

High-energy inelastic neutron scattering is used to resolve spin waves in La2CuO4. The corresponding long-wavelength velocity is 0.85±0.03 eV AÌ, well above previous bounds set by thermal neutron scattering. Within experimental error, conventional spin-wave theory gives an excellent description of the magnetic dynamics for momentum and energy transfers below 0.15 AÌ-1 and 0.1 eV, respectively. Doping with Ba changes the magnetic dynamics; the data indicate a combination of spin-wave softening and damping effects. © 1989 The American Physical Society.

A new family of rare earth-rhodium-tin intermetallic compounds, with the representative formula (RE)RhxSny, has been synthesized in single crystal form. The compounds containing the heavier rare earths are superconducting and those with the lighter rare earths are generally magnetic. The compound ErRh1.1Sn3.6 exhibits reentrant superconductivity with Tc = 0.97 K and Tm = 0.57 K as determined from ac magnetic susceptibility measurements. The synthesis and X-ray characterization of the series are described and the results of electrical resistivity, upper critical magnetic field, magnetic susceptibility, specific heat and neutron scattering measurements on the Er compound are given. © 1980.