Magnetic properties of the UNi_1-xPt_xGa solid solutions

The results of a structure and magnetization study of the UNi_1-xPt_xGa pseudoternary compounds are presented. Only limited solubility ranges 0≤x≤0.15 and 0.8≤x≤1 have been observed. The solid solutions preserve the ZrNiAl-type structure of the parent ternary compounds. The magnetization as a function of temperature and magnetic field indicates that the antiferromagnetic ground state of UNiGa is converted to ferromagnetism by only slight doping by Pt. On the other hand, the ferromagnetism in UPtGa seems to be nearly intact following the substitutions in the transition metal sublattice of up to 20% Ni. These results confirm that the antiferromagnetic ground state of UNiGa is a result of a delicate balance between antiferromagnetic and ferromagnetic components of exchange interactions mediated by the 5f-ligand hybridization. This state is very fragile with respect to application of magnetic field and substitution of Ni by other transition metals.