On the conduction band polarization in metallic systems with a periodic array of localized magnetic moments

It is shown that the indirect exchange between magnetic moments distributed in a periodic array and carried out through the conduction band results from the balance of a ferromagnetic component, static effect, and an antiferromagnetic one, polarization effect. The sign of the coupling mainly depends on the density of states at the Fermi level. For filled bands only the antiferromagnetic component exists (metallic superexchange) and, in particular, only for free electrons both components exactly compensate to each other, remaining the typical Ruderman-Kittel-Kasuya-Yosida ripple due to the oscillating character of the polarization. (C) 1996 American Institute of Physics.