Crossover from ferromagnetic to antiferromagnetic ground state in the (Ce1-xUx)(2)Pd2.05Sn0.95 system

The (Ce-1-U-x(x))(2)Pd2.05Sn0.95 solid solution has been investigated by me ans of x-ray powder diffraction and magnetization measurements. All the com pounds crystallize in the tetragonal U2Fe2Sn-type structure, P4/mbm space g roup. A crossover from ferromagnetic to antiferromagnetic behaviour at low temperature is observed around x similar or equal to 0.30: in the compositi on range 0 less than or equal to x 0.30, the Curie temperature T-C goes thr ough a maximum at x similar or equal to 0.10-0.15 whereas for 0.30 less tha n or equal to x < 1.0 the Neel temperature T-N increases continuously with x. Neutron powder diffraction performed on (Ce0.85U0.15)(2)Pd2.05Sn0.95 (x = 0.15) confirms the existence of a ferromagnetic structure below Te = 4.6( 1) K, with (Ce, U) magnetic moments parallel to the tetragonal c-axis. The magnetic phase diagram ((T-C, T-N) against x) of this system is discussed c onsidering a Ruderman-Kittel-Kasuya-Yosida model based on a non-spherical F ermi surface.