Antiferromagnetism and Spin Density Waves

Abstract

We deal with the antiferromagnetism (AF) of metals, the spin density waves, and the systems showing more complex magnetic structure in metallic magnetism in this chapter. We first present the Hartree–Fock theory of the gap-type AF at half-filling, and extend the dynamical CPA to the AF case to discuss the crossover from the band-gap type AF to the insulator AF due to the super exchange interactions. We overview the stability of the AF 3d metals on the basis of the realistic susceptibility calculations. Next we treat the spin density wave in Cr on the basis of the nesting model. In order to describe more complex magnetic structures, we introduce a microscopic theoretical framework called the molecular dynamics (MD) approach on the basis of the functional integral method and the recursion method. The latter method allows us to calculate the electronic structure of the systems without translational symmetry. In the last section of this chapter we present the Ginzburg–Landau theory to understand the complex magnetic structure and elucidate how the multiple spin density waves are stabilized in itinerant electron system.