No abstract

A crystal of VOMoO 4 was grown, which has a structure containing V-O-V-O linear chains along the c-axis. There a vanadium ion carries a spin of 1 2 per ion. The magnetic susceptibility was measured in the region from 2 to 300 K up to 55 kG. The temperature dependence shows a broad maximum around 100 K. This is a characteristic of a 1D antiferromagnet. Fitting to the uniform 1D Heisenberg model is very good in the higher temperature region. This suggests the onset of antiferromagnetic order around 100 K. At 34 K, however, χ shows a kink followed by a ferromagnetic hump at lower temperature. This suggests some magnetic phase transition. At 2 K a slight hysteresis was observed in the magnetic field dependence. The above behaviour was interpreted as the process of transfer from 1D to weak 3D interaction, according to lowering temperature. Lattice parameters increased with decreasing temperature below 100 K, then showed a hump around 30 K. This anomalous behaviour corresponds to the above magnetic results. It has been concluded that VOMoO 4 is a one-dimensional antiferromagnet. We also suggest the existence of a weak ferromagnetic ordered state such as canted or ferri-magnetism by the V-O pairs in the lower temperature region.

Single crystals of BaBiO3 and BaBi1-x Mo x O3 were grown by slow cooling of the molten mixture. The quality of the crystal was improved by addition of the excess BaCO3 of 20% to the mixture of starting materials with the cationic stoichiometry. Golden brown crystals grew, whose sizes ranged from 3×3×2 to 10×10×5 mm3. Quantitative analysis of BaBiO3 showed that the atomic ratios, Ba/Bi, ranged in 0.92–1.14. The oxygen stoichiometry was estimated as 2.83±0.05. The mass density was more than 96% of the calculated one. The ceramic compounds, Ba2BiInO6 and Ba2BiLaO6 were synthesized, too. It was found from the powder X-ray diffraction analysis, that the volume of Ba2BiInO6 is reduced by 5.3% of that of BaBiO3. The band structures of the compounds were examined by XPS. In Ba2BiInO6 4d level appeared below the valence band, while it was not observed in BaBi0.92Mo0.08O3.

Resonant inelastic x-ray scattering (RIXS) at the copper K absorption edge has been performed for heavily overdoped samples of La2−xSrxCuO4 with x = 0.25 and 0.30. We have observed the charge transfer and molecular-orbital excitations which exhibit resonances at incident energies of Ei = 8.992 and 8.998 keV, respectively. From a comparison with previous results on undoped and optimally-doped samples, we determine that the charge-transfer excitation energy increases monotonically as doping increases. In addition, the Ei-dependences of the RIXS spectral weight and absorption spectrum exhibit no clear peak at Ei = 8.998 keV in contrast to results in the underdoped samples. The low-energy (≤ 3 eV) continuum excitation intensity has been studied utilizing the high energy resolution of 0.13 eV (FWHM). A comparison of the RIXS profiles at (π 0) and (π π) indicates that the continuum intensity exists even at (π π) in the overdoped samples, whereas it has been reported only at (0 0) and (π 0) for the x = 0.17 sample. Furthermore, we also found an additional excitation on top of the continuum intensity at the (π π) and (π 0) positions.

No abstract