Aspects of spin dynamics and magnetic interactions

Non-collinear magnetic alignment is somewhat unusual for equilibrium, and those systems exhibiting such ground states are frequently `victims’ of competing forces. For non-equilibrium, or dynamical systems (e.g. T>0) non-collinear alignment is universal. We discuss such systems and present some basic formalism for evaluating from first principles the equation of motion and related relevant properties. Considerable discussion is also devoted to obtaining from first principles, parameters for model magnetic Hamiltonians. These models represent a convenient way to gain insight and to approximately evaluate magnetic interactions for very complex systems.