Muon trapping at monovacancies in iron

Positive-muon--spin-rotation experiments were performed on electron irradiated iron. A new defect-associated frequency is observed which is assigned to muons trapped at monovacancies. The hyperfine field at the vacancy site is -0.956 T at 140 K. The diffusion constant for ..mu../sup +/ in iron deduced from the trapping rate follows an Arrhenius law with an activation energy of 38 +- 3 meV between 90 and 190 K.