Spin polarized itinerant electrons in Ca2FeMoO6 double perovskites

We report on magnetic studies of the double perovskite Ca2FeMoO6 in its paramagnetic state. It is found that the effective magnetic moment, extracted from the Curie constant, is magnetic field dependent and it is smaller than that expected in a simple ionic scenario. These experimental results, which are in agreement with early reports on Sr2FeMoO6, are interpreted as a direct evidence of the antiferromagnetic coupling and polarization of the conduction band in these oxides. A simple mean field model accounts for these observations and enlightens the relevance of itinerant carriers on the strength of the magnetic coupling in these oxides.