Study of the electric quadrupole interaction at Ta impurities in rare earth metal hosts

The time differential perturbed angular correlation technique has been used to measure the electric fieldgradient (EFG) at the site of¹⁸¹Ta impurities in the heavy Rare Earth metals Gd, Tb, Dy, Ho and Er at room temperature. It is found that the ratio α ≡ ¦V _zz ^eff /V _zz ^lat ¦ between the measured EFGV _zz ^eff and the lattice EFGV _zz ^lat , which is known from lattice sum calculations, is in the order of α?300, suggesting that an important contribution to the EFG is due to electrons localized at the impurity. The ratio α is not constant throughout the Rare Earth series. It decreases from Gd to Tb and increases between Tb and Er. This behaviour is compared to the results of a previous investigation with the impurity Cd in the same hosts.