Nanowire Spin Hall Oscillators
The field of spintronics deals with the use of the spin degree of freedom of the electron and the spin current that arises from it. There are many static and dynamic applications for spin current whether it is supplied by spin polarized electric current from a magnetic layer or from pure spin current arising from spin orbit interaction such as the spin Hall effect. This dissertation focuses on the later where the spin Hall effect in platinum supplies a spin torque on an adjacent ferromagnetic layer and thereby excites auto-oscillations of its magnetization. Previous studies of magnetization dynamics excited by direct spin currents have demonstrated the existence of phase coherent auto-oscillations of magnetization in the 0-dimensional structures and its absence in the 2D case therefore the 1D case, a ferromagnetic nanowire, is presented here. This will cover the first instance of a micrometer scale STO and will show the excited modes are the edge and bulk spin wave eigenmodes of the nanowire. Additionally, the evolution of the auto-oscillation characteristics as the width of the wire is increased is shown which reveals the mechanisms of the auto-oscillation suppression as the system effective dimensionality crosses of over from the 1D to the 2D regime. Lastly, a novel type of spin torque oscillator with easy plane magnetic anisotropy is discussed; its properties are predicted via micromagnetic simulations and initial experimental data on this type of oscillator are presented.