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Spintronics has gone through substantial progress due to its applications in energy-efficient memory, logic and unconventional computing paradigms. Multilayer ferromagnetic thin films are extensively studied for understanding the domain wall and skyrmion dynamics. However, most of these studies are confined to the materials and domain wall/skyrmion physics. In this paper, we present the experimental and micromagnetic realization of a multilayer ferromagnetic spintronic device for neuromorphic computing applications. The device exhibits multilevel resistance states and the number of resistance states increases with lowering temperature. This is supported by the multilevel magnetization behavior observed in the micromagnetic simulations. Furthermore, the evolution of resistance states with spin-orbit torque is also explored in experiments and simulations. Using the multi-level resistance states of the device, we propose its applications as a synaptic device in hardware neural networks and study the linearity performance of the synaptic devices. The neural network based on these devices is trained and tested on the MNIST dataset using a supervised learning algorithm. The devices at the chip level achieve 90\% accuracy. Thus, proving its applications in neuromorphic computing. Furthermore, we lastly discuss the possible application of the device in cryogenic memory electronics for quantum computers.

Skyrmionic devices exhibit energy-efficient and high-integration data storage and computing capabilities due to their small size, topological protection, and low drive current requirements. So, to realize these devices, an extensive study, from fundamental physics to practical applications, becomes essential. In this article, we present an exhaustive review of the advancements in understanding the fundamental physics behind magnetic skyrmions and the novel data storage and computing technologies based on them. We begin with an in-depth discussion of fundamental concepts such as topological protection, stability, statics and dynamics essential for understanding skyrmions, henceforth the foundation of skyrmion technologies. For the realization of CMOS-compatible skyrmion functional devices, the writing and reading of the skyrmions are crucial. We discuss the developments in different writing schemes such as STT, SOT, and VCMA. The reading of skyrmions is predominantly achieved via two mechanisms: the Magnetoresistive Tunnel Junction (MTJ) TMR effect and topological resistivity (THE). So, a thorough investigation into the Skyrmion Hall Effect, topological properties, and emergent fields is also provided, concluding the discussion on skyrmion reading developments. Based on the writing and reading schemes, we discuss the applications of the skyrmions in conventional logic, unconventional logic, memory applications, and neuromorphic computing in particular. Subsequently, we present an overview of the potential of skyrmion-hosting Majorana Zero Modes (MZMs) in the emerging Topological Quantum Computation and helicity-dependent skyrmion qubits., Comment: arXiv admin note: text overlap with arXiv:1907.00957 by other authors