ABSTRACT
A high density of electrons increases the screening effect. If the electron density is not high, the screening will not be very effective, and the range of interaction will be large. In the actual devices, the thickness of the nonmagnetic metal is adjusted so that neighboring ferromagnetic sheets couple antiferromagnetically. The Hartree approximation attempts to simplify the problem to that of a single electron moving in an effective potential of all the other charges. The Hartree approach, being an independent electron treatment, misses out on physical effects that depend on the fact that the electrons are fermions obeying the Pauli principle. The Hartree-Fock approach also attempts to simplify the many-body problem, and unlike the earlier Hartree approach, builds in the Pauli principle.
