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The theory of quantum plasmas dates back to the first attempts of Wigner, Moyal and others to find a suitable formalism to describe many body quantum systems, and from this foundation a rich field has emerged. A plasma is a system consisting of many charged particles, and in a quantum plasma these particles have quantum mechanical properties, such as for example spin. Quantum properties of individual particles are often negligible on macroscopic scales, but due to collective interaction in the plasma certain phenomena arise that can only be explained by considering the fundamental quantum properties of the particles.

In this thesis kinetic descriptions, derived following the work of Wigner et al. and extended to also include particle spin, are employed to study various nonlinear phenomena related to the magnetic field generation and the ponderomotive force in quantum plasmas consisting of spin 1/2 particles. A specific model to study the special case of low temperature degenerate quantum plasmas by only considering dynamics on the surface of the velocity distribution sphere is also derived, and is applied to the problem of nonlinear Landau damping. Furthermore, by taking moments of the full kinetic theory a more nimble spin plasma fluid model is derived. This formalism is then applied to a variety of nonlinear problems involving the ponderomotive force and wave-wave interaction. Where possible the fluid model is shown to be in agreement with results derived from the considerably more complex full kinetic theory.