High-Velocity Skyrmions : Engineering, Memristors and Random Number Generation

Abstract

Non-collinear spin textures have become very important in both fundamental research and technology. One of the most interesting examples of these textures is the skyrmion. A skyrmion is a small, vortex-like spin pattern that has many unique characteristics. For instance, it is highly stable, meaning it can resist impurities and disturbances from outside. Skyrmions are also very mobile, have long lifetimes, and can be moved with very little current. These properties make them attractive for technological uses, such as in high-density memory devices (especially racetrack memory), neuromorphic computing, and random number generation. In the past decade, researchers have focused a lot on two types of skyrmions: Bloch skyrmions and N´eel skyrmions. These two types differ mainly in how their boundaries behave—Bloch skyrmions have helicoid walls, while N´eel skyrmions have cycloid walls. Scientists have found that these skyrmions can be created and controlled by adjusting factors such as anisotropy, dipolar interactions, and Dzyaloshinskii-Moriya interaction (DMI). In this thesis, we explore the exciting discovery of high-speed skyrmions that have a reduced skyrmion Hall effect. This finding is not only important from a fundamental research perspective but could also lead to an improved version of magnetic racetrack memory, which may be more practical than traditional designs. We conducted a detailed study on how changing the anisotropy affects the magnetic structure and the speed of skyrmions. Through this work, we found that these fast-moving skyrmions, with low Hall effect, can be applied in many technological areas. In one chapter, we highlight two promising applications of these skyrmions: first, their use in neuroid sigmoidal functions, and second, in mimicking the behavior of a synaptic memristor. In another chapter, we discuss how these fast-moving skyrmions could be effectively used to create a true random number generator, which has numerous potential applications in cryptography and data security.