Electronic structure of f.c.c. NiFe alloys, investigated by means of secondary ion emission

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Abstract
The secondary ion emission of f.c.c. Ni1-cFec alloys (0 < c ≤ 0.65) is investigated in relation with their electronic structure. The results obtained are interpreted in terms of an electronic density near the Fermi level : independent of concentration on nickel atoms, and rapidly increasing with cFe on iron atoms from c > 0.2. The concentration dependence of the iron ionization coefficient is well described by a simple local environment model where the magnetic state of an iron atom changes from strong ferromagnetic to polarized paramagnetic if surrounded by at least six iron nearest neighbours. Consequently the occurrence at the alloy Fermi level of a high density of states for the majority spin band is attributed to the existence of these paramagnetic iron atoms and not to a bulk transition of the alloy band structure to a weak ferromagnetic state