Exploring Magnetic Properties Of (K1-Xrbx)(2)U4o12

Magnetism in mixed-valent orthorhombic compound (K1-xRbx)(2)U4O12 with x = 0 and 0.15 was studied. U5+ ions in the (K1-xRbx)(2)U4O12 compound is responsible for the observed magnetic property. Both the samples exhibit two transitions, one around 25K and the other close to 10K. While the transition near 25 K is similar in both the samples, the transition near the 10 K is quite different in these two samples. It is seen that both the transitions are accompanied by thermal hysteresis. In addition, a prominent field dependent hysteresis loop observed below 10K transition and the magnetic relaxation suggest the role of energy barriers, perhaps originating from magnetocrystalline anisotropy. While it is clear that the transitions observed cannot be ferromagnetic, there exists a possibility that the transition near 10 K in Rb doped sample might be antiferromagnetic