Magnetic susceptibility of the intermediate-valence CeNi compound was measured under external pressure of 0.8, 1.05 and 1.25 GPa. The results obtained extend the pressure–temperature phase diagram of CeNi up to P = 2 GPa and Т = 300 K. It is shown that the pressure-induced phase of CeNi has a tetragonal symmetry. Specific heat measurements for the Ce1 − xLaxNi–CeNi–Ce1 − xLuxNi series demonstrate significant increase of the f-electron hybridization due to chemical pressure.

The structural disorder, heat capacity, resistivity, Hall effect, and magnetic susceptibility of polycrystalline chemical-vapor-deposited diamond irradiated with fast neutrons at temperature of (325 +/- 10) K at high fluences Phi=(1-5)x10(20) cm(-2) were investigated. Despite a significant increase in unit-cell volume (similar to 4.5%), the crystalline structure remains stable in this fluence range. The irradiation results in a paramagnetic contribution to magnetic susceptibility and to a strong (by 4 orders of magnitude) increase in heat capacity at low temperatures (T < 20 K) due to electron contribution with a T dependence characteristic of multilevel electron systems (the Schottky anomaly).

To impart high-temperature superconductivity to a homogeneous phase with the composition Nd1.85Ce0.15CuO4-y, equilibrium anneals were carried out under conditions that correspond to the low-oxygen boundary of the homogeneity region of this phase. Rietveld full-profile analysis in tandem with neutron diffraction was used to refine the structural parameters both for the obtained high-T-c phase and for the phase with the same cationic composition after thermally processing it in various modes that could not induce high-temperature superconductivity. A copper deficit was discovered in CuO2 layers, with the highest value of 11% observed in the sample annealed in air at 950 degreesC. A distinguishing feature of the high-T-c phase is the least distance between oxygen-deficient fluorite building blocks (Nd/Ce)(2)O2-y and almost oxygen-complete square CuO2 networks.

Structural distortions in high-T(c) 1-2-3 compounds under low temperature fast neutron irradiation are studied with neutron powder diffraction and compared with oxygen deficient samples. The results show the absence of essential charge transfer between the chains and planes for radiation-induced disorder and point to random defects to be responsible for the behavior of physical properties of high-T(c) superconductors.