We report an observation of metamagnetism in the 5f-electron heavy-fermion antiferromagnets UNi2Al3 at 78 T and U(Pd1-xNix)2Al3 at 30 T (42 T) for x=0.5 (x=0.75) using single-crystalline samples. The magnetization curves for U(Pd1-xNix)2Al3 (x=0.5 and 0.75) show a sharp increase at the metamagnetic transition (MMT) field Bm, strongly indicating their first-order nature. The obtained B-T phase diagram for x=0.5 suggests the possible presence of the tricritical point, while the MMT still occurs at high temperatures above TN from paramagnetic to polarized-paramagnetic states as a crossover. The results indicate that the antiferromagnetic order is closely connected to the MMT in U(Pd1-xNix)2Al3, but the metamagnetic behavior cannot be explained by the conventional spin flip of antiferromagnetic ordered moments. Our data for U(Pd1-xNix)2Al3 have revealed an empirical linear relation of Bm(x)âTχmax(x) and a scaling behavior in magnetic susceptibility of χ(T/Tχmax)/χmax, where Tχmax is the temperature of the susceptibility maximum [χmaxχ(Tχmax)]. Importantly, the critical value of the magnetic polarization at the MMT Mcr is roughly unchanged, although the value of susceptibility is notably suppressed with increasing x.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics