Covalent magnetism: An alternative to the Stoner model

We show that itinerant magnetism in a variety of transition-metal systems cannot be described by the familiar Stoner model (rigid-band theory). Magnetism as found in elemental anti-ferromagnets, in certain impurity systems (transition metals in transiton metals), and in certain transition-metal compounds is shown to arise from spin-dependent changes in the covalent interactions between the d states of neighboring transition-metal atoms.