Hyperfine interactions at Ta-181 in Hf2Co7

In this paper we report a time differential perturbed angular correlation ( TDPAC) study of hyperfine interactions at Ta-181 in Hf2Co7 compound. The TD PAC measurements have been performed in the temperature range 77-1023 K. Th e measured spectra showed broad distribution of hyperfine interactions up t o 388 K. Above this temperature, in a reversible manner, two nuclear electr ic quadrupole interactions (EQI) have been observed: at 393 K, nu (Q1) = 44 9.0(27) MHz, eta (1) = 0.00(4) and nu (Q2) = 144.7(41) MHz, eta (2) = 0.44( 2). Since the Curie temperature for this compound is known from the literat ure to be around 420 K, only magnetic order transition could be responsible for such an observation. However, the measurements of magnetization did no t exhibit any drastic change in this temperature range.