Negative muon spin precession in ferromagnetic iron and the hyperfine anomaly

The hyperfine field (B μ hf ) at the negative muon μ− in ferromagnetic iron was investigated by means of the zero-field μ− spin precession technique. In the temperature range 320–690 K,B μ hf for μ− Fe departs from the magnetization curve of pure iron in the same way as the hyperfine field seen by a55Mn impurity in dilute MnFe measured by NMR. The hyperfine anomaly for μ− Fe relative to dilute (1.5 at.%)55Mn in iron is found to be −0.9(3)% and temperature independent over the temperature range investigated.