Abstrakt
Electrical resistivity rho(T) of the 5f-ferromagnet UGa2 was investigated on single-crystalline samples as a function of pressure and magnetic field. Under quasihydrostatic pressure the Curie temperature monotonously increases from T-C = 124 K up to 154 K at p = 14.2 GPa after which it turns down steeply and reaches T-C = 147 K at p = 15.2 GPa.
At 20 GPa the compound is already nonmagnetic. This dramatic variation is compatible with the exchange interactions mediated by the 5f hybridization with the non-f states.
The external pressure first enhances the exchange coupling of the 5f moment but eventually suppresses the magnetic order by washing out the 5f moments. Such a two-band model is adequate for the weakly delocalized 5f states.
The external pressure gradually suppresses the spin-disorder resistivity, which reaches very high. values (300 mu Omega cm) above T-C in UGa2. This leads to the crossover from the initial negative to the positive d rho/dT in the paramagnetic state.