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NewACu3V4O12(A=Gd, Tb, Er) phases have been prepared at high pressure and high-temperature conditions (P∼8–9 GPa,T∼1000°C) in a toroid-type high pressure cell. These compounds crystallize in the cubic symmetry with a perovskite-like structure. At ambient pressure, they are paramagnetic and have activation-type conductivity. The effect of high pressure (10–50 GPa) on the electrical properties of the materials was analyzed in the temperature range from 78 to 300 K. Pressure ranges of the transition from activation type to metallic conductivity have been determined. The crystal structure ofACu3V4O12(A=Gd, Tb, Er) was found to be stable up to 50 GPa. [ABSTRACT FROM PUBLISHER]

Abstract: We carried out experimental SQUID and EPR studies together with LSDA + U quantum calculations of the electronic spectra and spin density distribution for dimeric crystals [(L)2Cu2Cl2(H2O)], where -phenyl-3-(2-pyridyl)-5-trifluoroacetylmethylidene-4,5-dihydro-1,2,4-triazine. We found experimentally and confirmed numerically that , , and , are affected by intradimer spin polarization of the 1,2,4-triazine fragment and interstack exchange interactions. The interplay between -stacking and Cu1–Cu1# antiferromagnetic coupling causes a structure instability which ends up by spontaneous destruction of the crystal at 2 K under influence of DC and AC magnetic fields. [Copyright &y& Elsevier]