STIFFNESS CONSTANT OF STRONG FERROMAGNETIC NI-BASED ALLOYS, MEASUREMENTS IN NICO-INTERPRETATION WITHIN BAND MODELS

The stiffness constant D has been measured in NiCo alloys (5.21 and 50 per cent cobalt) by using inelastic neutron scattering. The authors outline the importance of correcting apparatus effects to get a precise determination of D and compare their results to previous measurements. They show that the D behaviour in NiCo can be accounted for in the RPA theory even within a rigid band model if one assumes a large value for the effective interaction parameter U(U approximately=7 eV). The case of NiCo is compared to those of NiFe and NiMn in a CPA-RPA model.