First-principles calculations of magnetic interactions in correlated systems

We present a method to calculate the effective exchange interaction paramet ers based on the realistic electronic structure of correlated magnetic crys tals in local approach with the frequency dependent self-energy. The analog of "local force theorem" in the density-functional theory is proven for hi ghly correlated systems. The expressions for effective exchange parameters, Dzialoshinskii-Moriya interaction, and magnetic anisotropy are derived. Th e first-principles calculations of magnetic excitation spectrum for ferroma gnetic iron, with the local correlation effects from the numerically exact QMC scheme, are presented.