NONMAGNETIC-MAGNETIC CROSSOVER IN THE URU1-XPDXGA SYSTEM

X-ray and neutron diffraction, magnetic susceptibility, and magnetizat ion measurements were performed on URu1-xPdxGa solid solutions (x = 0. 0-1.0). They crystallize in the hexagonal HoNiAl-type structure with s pace group P (6) over bar 2m. The concentration dependence of the latt ice parameters deviates from Vegard's law, showing anomalies at x = 0. 2 and 0.8. The magnetic phase diagram consists of three different conc entration regions. Below x = 0.1 the system is nonmagnetic down to 1.7 K. In the region 0.1<x<0.8 the magnetic state of these compositions a l higher temperatures can be considered as a ferromagnetic state with a transition temperature T-C that goes through its maximum value of 78 .4 K at x=0.5. At lower temperatures this state seems to be more compl ex and requires further studies. For x greater than or equal to 0.8 th e magnetic state of the system also changes with temperature, but the magnetic ground state has been established as antiferromagnetic. The m agnetic behavior of the URu1-xPdxGa sold solutions as other similar al loys is governed by a change in both the unit-cell volume and the numb er of d and/or sp electrons in the system. [S0163-1829(97)06338-8].