Electronic and magnetic properties of Fe-Cu superlattices

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Abstract
The electronic and magnetic properties of Fe/Cu superlattices grown in the (111) direction, for which Fe takes the FCC structure, are studied with a parametrized tight-binding Hamiltonian. The splitting between majority and minority d bands is related to an effective exchange parameter J that we adjust to obtain within our model the bulk magnetization for BCC Fe. As the magnetization of bulk FCC Fe is very sensitive to this parameter we study the magnetic properties as a function of it. We find that the 2Fe/2Cu superlattice is possibly ferromagnetic and that 3Fe/3Cu has more than one stable state (paramagnetic, ferromagnetic or ferrimagnetic) with quite similar energies. As recent experimental results detect a small magnetic moment for this last superlattice, comparison with the calculations suggest that they are ferrimagnetic. Comparison with calculations for 2Fe and 3Fe FCC(111) free-standing slabs show that the 2Fe/2Cu and 3Fe/3Cu superlattices behave as low-dimensional systems, the effect of Cu being to slightly reduce the magnetic moment per atom of Fe with respect to a free-standing slab.