Ferromagnetism in the UCo1-xRuxAl quasiternary intermetallics

Publisher Website
Google Scholar
Abstract
We report the structure and magnetic investigations of the quasiternary UCo1-xRuxAl compounds crystallizing in the hexagonal structure of the ZrNiAl type. A large deviation from linearity is observed in the concentration dependence of lattice parameters, positive for a and negative for c, whereas the unit-cell volume V obeys Vegard's law satisfactorily. The nonlinearity is explained by a preferential occupation by the Co and Ru atoms of the two non-equivalent positions of the transition metal in the lattice. Although UCoAl and URuAl are paramagnetic down to low temperatures, ferromagnetism is observed in a wide concentration range of quasiternary solid solutions UCo1-xRuxAl. Both the Curie temperature and the spontaneous magnetization reach their maximum values of 60 K and 0.6μB (formula unit)−1 respectively in UCo0.7Ru0.3Al. The samples in the Ru concentration range 0.5 ≤ x ≤ 0.7 exhibit a second phase transition in the ordered state, indicated by anomalies in temperature dependence of both the spontaneous magnetization and the ac susceptibility. The development of magnetism is discussed in the framework of the anisotropic 5f-ligand hybridization and the direction dependent exchange interactions mediated by it.