Effects of alloying and pressure on magnetic properties of (U1−xThx)3Al2M3 (M = Si and Ge)

The pressure derivative dTC/dP was evaluated from measurements of the paramagnetic susceptibility of (U0.95Th0.05)3Al2M3 alloys (M = Si and Ge) under uniform pressure in order to estimate the chemical pressure effect on TC. Our results show that the decrease of the unit cell volume under pressure is followed by decrease of Θ (≈TC). As it was evaluated from X-ray study, the substitution of U by Th leads to a nearly linear increase of the unit cell volume V, i.e. to negative chemical pressure effect. The chemical pressure effect appears to be of the same order as the total change of TC induced by hydrostatic pressure in these alloys but opposite in sign. The decrease of TC with alloying is presumably caused by a change of 5f state hybridization with conduction electrons.