111Cd-time differential perturbed angular correlation study of pressure effect on the hyperfine quadrupole interaction in the UGe2 cubic phase

The time differential perturbed angular γγ-correlation method (TDPAC) has been used to study the hyperfine quadrupole interaction (HQI) of 111Cd probe nuclei introduced in the novel cubic phase of UGe2 (the AuCu3 crystal lattice). The HQI parameters have been measured as a function of pressure up to 8 GPa. At normal pressure the TDPAC spectrum is described by a single quadrupole frequency of 101.8 MHz. The quadrupole frequency increases with pressure to 118.4 MHz at 5.5 GPa. At a pressure of 7.0 GPa the TDPAC spectrum becomes complex and can be fit by two characteristic quadrupole frequencies: ν1Q = 117 MHz and ν2Q = 147 MHz. The appearance of the second quadrupole frequency of 111Cd probe nuclei has been ascribed to a signal from 111Cd probes in U sites, which become effective due to a structural phase transition in UGe2.

► New cubic phase of UGe2 has been synthesized.
► TDPAC method has been used to measure spectra at various temperatures and pressures.
► Change of the spectra has been ascribed to a structural phase transition at 7.0 GPa.