High-pressure study of ferromagnetic UxM1-x (M = Pt, Ir) compounds

Measurements of the electrical resistivity under pressure to 20 kbar and th e magnetization and specific heat at zero pressure were performed on the it inerant ferromagnetic compounds UxPt1-x (0.50 less than or equal to x less than or equal to 0.54) and UIr. The UxPt1-x materials order magnetically at T-C1 similar to 18 K and T-C2 similar to 27 K and the ordering temperature s exhibit a small pressure dependence. Above 10 kbar, only the lower-temper ature phase is present. The Curie temperature of UIr, on the other hand, de creases from 47 K at ambient pressure to 27 K by 19 kbar, and the critical pressure Pc for the complete suppression of ferromagnetism is estimated to be similar to 40 kbar. UPt and UIr obey the Kadowaki-Woods relation and hav e Wilson ratios of order unity and could be classified as moderately heavy- fermion ferromagnetic materials.