Magnetism of U4(Ru1-xOsx)7Ge6 solid solutions

U4Ru7Ge6 orders ferromagnetically at low temperature, displays a Kondo-like resistivity behaviour and has heavy-fermion properties, whereas U4Os7Ge6 is a Pauli paramagnet. We measured the magnetisation and susceptibility of eleven U-4(Ru1-xOsx)(7)Ge-6 compounds (0 less than or equal tox less than or equal to1) with steps of 0.1) between 2 K and 300 K under external magnetic fields up to 6.5 T, using a SQUID magnetometer. For the solid solutions, we observe clearly a rapid loss of magnetism for increasing x: the ordering temperature decreases hom 12 K for x=0 down to less than 2 K for x=0.3, whereas compounds with higher x are paramagnetic. The susceptibilities of all compounds follow a modified Curie-Weiss law. Values of Curie-Weiss parameters are discussed in the frame of the Doniach model. (C) 2001 Elsevier Science B.V. All rights reserved.