Low-temperature heat capacity and magnetism in (U1-yLny)O2 and (U1-yAmy)O2 (y= 0.01 - 0.05) solid solutions: Effects of substitution and self-irradiation

The low-temperature heat capacity of lanthanide-doped (La, Nd) and americium-doped UO2 samples was measured by calorimetry. The results showed a strong effect on the antiferromagnetic Cp anomaly as a result of crystal lattice substitution, defects resulting from selfirradiation, and electron interaction. It was found that the substitution of trivalent ions (La3þ, Nd3þ, Am3þ) leads to a split of the λ peak, for which we hypothesize that the clustering of the trivalent ions with the charge compensator pentavalent U5þ can play a role. The overall behavior is confirmed by magnetization measurements using SQUID. The observed differences between La3þ, Nd3þ, and Am3þ are attributed to the f –f exchange interaction. 241Am decay causes in addition self-irradiation effects (point defects), and reduces Néel temperature, peak intensity, and magnetic entropy as a function of decay (accumulated α dose). The observed effects are similar to 238Pu-doped UO2, the slight differences being attributed to a higher degree of disorder in the Am material.

GRIVEAU Jean-Christophe;  VIGIER Jean-Francois;  POPA Karin;  VALU Octavian;  COLINEAU Eric;  KONINGS Rudy; 

2022-11-09

AIP PUBLISHING

JRC130203

0021-8979 (online),   

https://aip.scitation.org/doi/pdf/10.1063/5.0112674,    https://publications.jrc.ec.europa.eu/repository/handle/JRC130203,   

10.1063/5.0112674 (online),