Basic Concepts

Abstract

This chapter contains the basic notions and concepts used in the subsequent chapters. After a short recapitulation of the formalism used for the description of ensembles of polarized electrons (Sect. 2.1), the two main types of spin-dependent interactions are discussed: Spin-orbit interaction (Sect. 2.2) and exchange interaction (Sect. 2.3). Spin-orbit interaction is treated within the context of electron scattering from a central potential. Exchange interaction is demonstrated to arise from the Pauli principle in the interaction of two spin-1/2 particles. Section 2.4 describes the concepts developed to calculate spin-dependent elastic diffraction from non-magnetic and magnetic surfaces. The spin-dependent LEED state defined there reappears in Sect. 2.5 in the context of spin-polarized photoemis-sion. Using the information contained in the electron spin is shown to considerably enlarge the knowledge of the electronic band structure of magnetic and nonmagnetic solids. A brief discussion of spin-dependent inelastic processes closes the chapter. The emphasis is on a description of the physical processes and of the assumptions underlying the theoretical treatment. For more detailed discussions reference is made to several excellent review papers or books.