THE TEMPERATURE DEPENDENCE OF THE MAGNETIC HYPERFINE FIELD AT 57Fe IN CHROMIUM-MANGANESE ALLOYS

The magnetic hyperfine fields for Fe in alloys of chromium with manganese additions have been obtained as functions of temperature and manganese concentration using the Mossbauer Effect. With increasing manganese concentration the mean hyperfine field at 4.2K decreases to a minimum for ∼10% manganese and increases slightly for 40% manganese. Near neighbour effects on the Fe57 resonance are small, suggesting the rigid band model is appropriate for these alloys. All samples gave unusual temperature dependences of the magnetic hyperfine field, there being a temperature region where the field is very small, with large fields above and below this temperature. The behaviour of the hyperfine fields as functions of temperature and concentration can be interpreted in terms of a weak exchange coupling between the iron magnetic moments and neighbouring chromium moments (giving a Brillouin function dependence on the host magnetization and the temperature) plus a contribution of the opposite sign proportional to the host magnetization and which is attributable to a conduction s electron polarization.