Ferrite Magnetism

Abstract

This chapter first briefly introduces the first-principles calculations. The focus is clearly on the exchange correlation, because it will directly affect the calculated magnetic properties, such as exchange integrals. The chapter then explains the application of first-principles calculations to ferrites, a family of practical magnetic materials. It focuses on the first-principles calculations of exchange integral and magnetic anisotropy, both of which are important magnetic properties impacting the applications of ferrites. Before further discussion, the chapter puts a brief remark on local magnetic moment by first-principles calculations. In spite of the particular definition of magnetization in density functional theory, a fact about ferrites is that most of them are good insulators, which implies that magnetization densities are localized around magnetic ions. Thus, the local magnetic moment, or local spin, is well defined, and the Heisenberg model is valid. In fact, the first-principles calculations of exchange integrals are based on the Heisenberg model.