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 ${\mu }^{+}$ in iron deduced from the trapping rate follows an Arrhenius law with an activation energy of 38±3 meV between 90 and 190 K.

• Received 9 November 1982

DOI:https://doi.org/10.1103/PhysRevB.27.2674