Introduction

Cobalt oxides are known to exhibit peculiar physical/chemical

properties, aswell as being suitable candidates forwide applications

such as electrode materials, thermoelectric materials, solid oxide

fuel cells, and so forth. Such properties are closely related to

versatility of the cobalt cations to adopt different valences and

spin states in the narrow energy range, which associate with the

charge and spin configuration on 3d orbitals, respectively. In this chapter, the charge, spin, and orbital for the 3d electron system are introduced, and then their role in the transport properties under

external perturbations is formulated.