Investigations on the magnetization dynamics of ferromagnetic thin films

Abstract

Spintronics is a multidisciplinary field whose central idea is to manipulate spin degrees of freedom in nano-devices. Many theoretical and experimental researches have nurtured the development of novel devices, hence high density data storage systems, spin logic circuits, magnetic sensors and many new devices in communication systems have mushroomed. In this scenario, Magnetic Tunnel Junction (MTJ) is a potential candidate to explore, since it is an essential component in read/write heads, magnetic storage and also in microwave oscillators. This thesis is based on the investigations carried out in two different MTJ structures. Magnetization dynamics in two different multilayer systems is investigated analytically and numerically by solving the associated Landau- Lifshitz-Gilbert- Slonczewski (LLGS) equation. Dual barrier-Magnetic Tunnel Junction (MTJ) and Composite free layer-Magnetic Tunnel Junction have been modeled as an extended LLGS equation and investigated. Dynamics of the magnetization is studied by plotting the trajectories of the spin components of the free layer. Initially Dual barrier-(MTJ) is modeled by its associated LLGS equation which includes inter/intra layer magnetic interactions. The dynamical equation is transformed stereographically on to a complex plane and it evolves as Cubic Quintic Nonlinear Schrodinger (CQNLS) equation. Using Hirota s technique, CQNLS equation is bilinearised and the excitations are found to be soliton solutions. newline