Micromagnetic modeling of spintronic devices: from uniform state to skyrmion

Abstract

Spintronics is a branch of Physics which has attracted a lot interest over the past 30 years. Differently from Electronics, that entrusts the binary encode to the electron charge, Spintronics considers both charge and spin momentum of electrons. This bond between electron charge and spin allows to alter the electronic transport by spins, and, vice versa, to affect the magnetic properties by electron charges. In this way, it has been possible to design and make devices characterized by nanometer dimensions, low energy consumption, non-volatility, large speed, high scalability, and compatibility with nowadays’ electronic industry. Spintronic devices are typically composed of a trilayer where a nonmagnetic spacer is sandwiched between two ferromagnets. The magnetization of one of them can be manipulated, not only by external applied fields, but also by an electrical current perpendicularly injected into the stack. This additional degree of freedom in controlling the magnetization dynamics has given rise to several technological applications of spintronic devices, as magnetic storages, which have been already commercialized, microwave oscillators, which are the smallest oscillators existing in nature and microwave detectors, whose sensitivity has already overcome the one of Schottky diodes. A strategy to improve the performances of spintronic devices concerns the use of non-uniform configurations of the magnetization, among them skyrmions have shown promising features. The main characteristic is the topological protection which makes skyrmions very stable and hard to be wrecked. This thesis shows the results achieved by means of micromagnetic simulations on magnetic storages, microwave oscillators and detectors based on both a uniform and a skyrmion state of the magnetization