THEORY OF ITINERANT FERROMAGNETS EXHIBITING LOCALIZED-MOMENT BEHAVIOR ABOVE CURIE POINT

By using a functional integral formulation of the theory of itinerant ferromagnets above the Curie point, we show that for strong Coulomb interaction U, there are localized moments exhibiting a characteristic Curie-law susceptibility with the correct free spin-1/2 limiting value of the Curie constant. For weak U the same formulation gives a Pauli-like susceptibility, again with the proper limit, while for intermediate values the theory gives a smooth interpolation between the extreme cases. © 1969 The American Physical Society.