A Theory of Nearly Ferromagnetic Semiconductors

Abstract

Magnetic and thermal properties of nearly ferromagnetic semiconductors are investigated on the basis of our spin fluctuation theory of itinerant electron systems. The couplings among the spin fluctuation modes of general amplitudes are taken into account by using a functional integral formalism within a local approximation, introducing a simple model for the local density of states. The negative mode-mode coupling at low temperatures and the saturation of the amplitude of local spin fluctuations at high temperatures seem to explain peculiar magnetic and thermal properties reported on FeSi.