ABSTRACT
This chapter provides an introduction into the physical ideas on which understanding of permanent magnetism based. Besides fundamental phenomena, such as spin-orbit coupling and ionic magnetism, the key issue is the microscopic origin of magnetization M(r) in solids that is the formation of atomic spin and orbital momenta as well as finite-temperature inter-atomic ordering. Magnetism involves both atomic-scale electrostatic interactions and long-range magnetostatic dipole interactions. The chapter presents some fundamental topics, electromagnetism, angular momentum algebra, spin-orbit coupling, exchange and magnetostatics rather than to investigate particular aspects of permanent magnetism. Electromagnetic fields created by atomic matter obey the relativistic, space-time symmetric Maxwell equations. First, separate the electro-dynamic aspect of magnetism from its atomic origin by formulating the magnetostatic equations in terms of dipolar fields. Maxwell’s equations describe phenomena such as light propagation, electromagnetic induction and magnetic flux creation by solenoids, as well as permanent magnetism.
