| Under highly idealized assumptions the model for a thin ferromagnetic film supports a family of large amplitude, localized waves in the magnetization, termed droplet solitons [Kos90; HS12]. In physical systems, these highly idealized assumptions cannot be met, yet there have been recent observations of structures similar to droplet solitons in experiments where both damping and spintransfer torque effectively cancel each other out [Moh13;Mac14]. Typically, damping and forcing are small and may be viewed as a perturbation of the classical model. This thesis derives a general framework for investigating such perturbations, as well as many others, using the techniques of soliton perturbation theory. The method utilized here is generalized to a broad class of Hamiltonian systems which includes the model of magnetic systems studied here. Also derived is an approximate, analytical representation of the droplet soliton, which is valid for low frequencies and low velocities. Leveraging the approximate droplet, many analytical results can be obtained for quite complex systems. A wide range of physically relevant effects are explored determining the particle-like dynamics of the droplet. The most important of these applications is the nanocontact spin torque oscillator which corresponds to the experimental conditions where the droplet has been observed. The framework here is used to probe the existence and stability of the droplet in certain parameter regimes utilizing classical tools from dynamical systems theory. The validity of the approximate theory is tested by comparison with careful numerical experiments. |
