Zelinskiy A. Interaction of components in the U-{Fe, Co, Ni}-Ga ternary systems

The thesis is devoted to the investigation of the components interaction in the U-{Fe, Co, Ni}-Ga ternary systems. The isothermal sections of the phase diagrams were constructed at 870 K over the whole concentration range using X-ray diffraction and EDX-analysis. The existence of 9 ternary compounds was confirmed. The existence of 23 new ternary compounds was found and their crystal structures were determined. The crystal structures of the compounds belong to 17 structure types; 7 from them (U11Ni16, U5Co11Ga21, U11Co17Ga32, U1.81Co14.30Ga3.08, U1.5Co8.0Ga9.5, U2.79Co12.40Ga3.12 and U0.88Ni3.76Ga1.91) are new. The homogeneity regions of 4 ternary compounds and the limits of solid solutions on the basis of 4 binary compounds were determined. The magnetic measurements for the ternary compound UNi5-xGax (structure type CaCu5) revealed a broad maximum at Т ~ 60 K typical for heavy-fermion systems. Additional peak at Т ~ 26 K (ТN ~ 23 K) is possibly due to an antiferromagnetic coupling of the uranium spins. Anomalies in the specific heat versus temperature observed at 30.5 K for U16.5Ni40Ga43.5 confirm the indications of the onset of antiferromagnetic order. The enhanced gamma-value of ~110 mJ/mol·K^2 suggests that this is a strongly correlated electron system.