Evidence of screening charge depression in the vicinity of chromium and manganese impurities in aluminium at low temperature

Electric field gradients (EFG) experienced by aluminium nuclei around a substitutional impurity are closely related to the screening charge produced by conduction electrons. The experimental values of the EFG on the neighbouring shells of nuclei around chromium or manganese are obtained by the field cycling double resonance technique at 1.4K. These values compared with the EFG data obtained in Al-Sc clearly indicate the existence of a preasymptotic attenuation of the screening charge, due to the proximity of the virtual bound state to the Fermi level.