Anisotropic thermal expansion and electronic transitions in the CoBO ludwigite.

The investigations of the crystal structure, magnetic and electronic properties of CoBO at high temperatures were carried out using powder X-ray diffraction, magnetic susceptibility, electrical resistivity, and thermopower measurements. The orthorhombic symmetry (Sp.gr.

Contribution of the Multiplicity Fluctuation in the Temperature Dependence of Phonon Spectra of Rare-Earth Cobaltites.

We have studied, both experimentally and theoretically, the unusual temperature dependence of the phonon spectra in NdCoO, SmCoO and GdCoO, where the Co ion is in the low-spin (LS) ground state, and at the finite temperature, the high-spin (HS) term has a nonzero concentration nHS due to multiplicity fluctuations. We measured the absorption spectra in polycrystalline and nanostructured samples in the temperature range 3-550 K and found a quite strong breathing mode softening that cannot be explained by standard lattice anharmonicity. We showed that the anharmonicity in the electron-phonon interaction is responsible for this red shift proportional to the nHS concentration.

Effect of Multiplicity Fluctuation in Cobalt Ions on Crystal Structure, Magnetic and Electrical Properties of NdCoO and SmCoO.

The structural, magnetic, electrical, and dilatation properties of the rare-earth NdCoO and SmCoO cobaltites were investigated. Their comparative analysis was carried out and the effect of multiplicity fluctuations on physical properties of the studied cobaltites was considered. Correlations between the spin state change of cobalt ions and the temperature dependence anomalies of the lattice parameters, magnetic susceptibility, volume thermal expansion coefficient, and electrical resistance have been revealed.

Upgrading the LANSCE accelerator with a SNS RF-driven H ion source.

The LANSCE accelerator is currently powered by a filament-driven, biased converter-type H ion source that operates at 10%, the highest plasma duty factor for this type of source, using only ∼2.2 SCCM of H. The ion source needs to be replaced every 4 weeks, which takes up to 4 days.

Effect of Oxygen Nonstoichiometry on Electrical Conductivity and Thermopower of GdSrFeO Ferrite Samples.

The behavior of the resistivity and thermopower of the GdSrFeO ferrite samples with a perovskite structure and the sample stability in an inert gas atmosphere in the temperature range of 300⁻800 K have been examined. It has been established that, in the investigated temperature range, the thermoelectric properties in the heating‒cooling mode are stabilized at ≥ 0.21.