Unusual phase transition of UGa3 observed by Ga NQR

In an antiferromagnetic compound, UGa3 (TN=67 K), with the cubic AuCu3 type structure, an unusual behavior near TN has been found by Ga nuclear quadrupole resonance (NQR) measurements. In the paramagnetic state above 72 K, a single 69Ga NQR line is observed at 19.8 MHz. The NQR line rapidly vanishes in the vicinity of 70 K, and another NQR spectrum appears with a double peak of 17.2 and 16.55 MHz which has no temperature dependence between 63 and 70 K. Some splittings due to an internal field are observed only below 63 K. This result suggests a transient modification of the 4 p-state hybridized with 5 f-electrons and a complicated situation on the magnetic structure. (author)