SPIN-DENSITY IN FERROMAGNETIC NICKEL - A MAGNETIC COMPTON-SCATTERING STUDY

The magnetic Compton profiles (MCPs) measured in the [100], [110], [11 1] and [112] directions in single-crystal nickel with an incident phot on beam of energy 224 keV are presented and discussed. The momentum re solution achieved, of 0.43 atomic units, improves on previous studies by almost a factor of two, and facilitates the interpretation of the M CPs in terms of the underlying spin-dependent momentum densities. Calc ulations have been performed using the linear muffin-tin orbital metho d, within both the local spin-density approximation (LSDA) and the gen eralized gradient approximation (GGA). Comparison with experiment reve als the limitations of the LSDA at tow momentum, where the GGA is bett er able to reproduce the contribution of the s- and p-like electrons. All of the calculations overestimate the moment associated with the d- like electrons, for momenta corresponding to the first Brillouin zone. We also confirm the existence of the so-called Umklapp shoulders, whi ch derive from the Fermi surface topology.