摘要：The low-temperature heat capacity of (U 1-y Th y )O 2 and 238 Pu-doped UO 2 samples were determined using hybrid adiabatic relaxation calorimetry. Results of the investigated systems revealed the presence of the magnetic transition specific for UO 2 in all three intermediate compositions of the uranium-thorium dioxide (y = 0.05, 0.09 and 0.12) and in the 238 Pu-doped UO 2 around 25 K. The magnetic behaviour of UO 2 exposed to the high alpha dose from the 238 Pu isotope was studied over time and it was found that 1.6% 238 Pu affects the magnetic transition substantially, even after short period of time after annealing. In both systems the antiferromagnetic transition changes intensity, shape and Néel temperature with increasing Th-content and radiation dose, respectively, related to the increasing disorder on the crystal lattice resulting from substitution and defect creation.
