Fe - Co - Ni thin films

Binary NiFe, NiCo, and FeCo films and ternary NiFeCo films have been investigated over a large range of alloy composition. Measurements were carried out for the uniaxial anisotropy K
u
, the structure constant
S
, and the wall coercive force H
w
. It is qualitatively shown that the uniaxial anisotropy is mainly caused by directional ordering of unequal pairs of atoms. The model of directional pair ordering of equal pairs, as usually discussed in the literature, appears incorrect. The strongest contribution comes from FeCo pairs, the next from NiCo pairs, while the influence of NiFe pairs seems to be small. Investigation of well prepared ternary films will allow the determination of the six anisotropy constants which are related to the six possibilities of pairing three different sorts of atoms. The dependence of the uniaxial anisotropy as given by the experiment is shown by a plot in the ternary alloy diagram. The relation for the coercive force
H_{w} \propto K_{u}^{1/4}D^{1/2}M_{w}^{-1} S
was verified over the whole range of alloy composition. A plot of H
w
in the ternary alloy diagram is also given.