Interaction of vacancies with impurities in iron

Muon Spin Rotation (γSR) experiments were performed on diluted (400 ppm) iron alloys. The annealing behaviour of electron irradiated samples was studied. We found that below T_A=200 K, muons are trapped at isolated vacancies (ν=30 MHz). Around 200 K the isolated vacancies disappear and, in some of the samples, a new signal, which is assigned to a vacancy-impurity pair, shows up. From the disappearance of this signal, the vacancy-impurity binding energy is derived.