TRANSITION METAL INDUCED HIGH SPIN POLARIZATION IN ZIGZAG SiCNT AND BLACK ARSENIC PHOSPHORUS: MATERIALS FOR SPINTRONIC APPLICATIONS

Abstract

This thesis explores the potential of transition metal-induced high spin polarization in zigzag Silicon Carbide Nanotubes and Black Arsenic Phosphorus for spintronic device applications. Spintronics, an emerging field of technology, leverages the intrinsic spin of electrons along with their charge to revolutionize data storage, magnetic sensing, and advanced computing technologies. Despite advancements in spintronics, several challenges persist, including limited spin diffusion lengths, finite defect densities, low energy density of existing materials, bias-dependent decrease in tunnel magnetoresistance and temperature sensitivity of MTJs. Additionally, materials like SiCNTs and b-AsP possess excellent properties such as tunable band gaps and thermal stability but lack intrinsic magnetism, hindering their direct application in spintronic devices. This research employs density functional theory calculations to study the adsorption of transition metals on SiCNTs and b-AsP. The investigation focuses on the electronic and magnetic properties of these materials upon transition metal adsorption. Different transition metals (Ag, Co, Cr, Cu, Fe, Mo, Ti, Zr) are adsorbed on various chiralities of SiCNTs (zigzag (4,0), (6,0), and (8,0)) and pristine b-AsP to analyze their impact on spin polarization and magnetization. Computational simulations and optimizations are performed to evaluate the stability and feasibility of TM adsorption on these materials. The study of SiCNTs reveals significant changes in their electronic and magnetic properties upon TM adsorption. The adsorption of Co, Cr, Fe, Mo, and Ti on SiCNTs induces substantial magnetic moments, transforming the non-magnetic SiCNTs into ferromagnetic (FM) or half-metallic ferromagnetic (HMF) states. The strength of the induced ferromagnetic behaviour varies with the various transition metals and is then related to the calculated magnetic moment in the adsorbed structure. The Cr adsorbed (8,0) SiCNT indicated strong HMF behaviour with a magnetic moment of 5.4 μB. These findings suggest that TM adsorption can significantly enhance the spintronic properties of SiCNTs and will be helpful in designing devices like spin valves, MTJs, and MRAMs in the field of spintronics. The electronic and magnetic properties of two-dimensional black Arsenic Phosphorus (b-AsP) on adsorption of Transition Metals (TM) on its surface are investigated using density functional theory (DFT) based on first principles calculations. The spin-density of states (s-DOS) and the bandstructure of all the transition metals adsorbed structures have been plotted, which shows their transformation from non-magnetic to magnetic behaviour. The results suggest that pristine b-AsP, which is a non-magnetic semiconductor, turns into an HMF on the adsorption of Co, Fe and Ti, and it turns into v an FM on the adsorption of Cr and Zr. The total magnetic moments were also calculated to further support our results and findings. Strong magnetic moments were observed for Cr, Fe, and Ti adsorbed b-AsP structures. Ag, Cu and Mo adsorption over b-AsP results in non-magnetic metallic characteristics with very weak magnetic moments. This transformation from a non-magnetic semiconductor to a magnetic HMF or FM material demonstrates the potential use of b-AsP in designing spin magnetic devices for various spin-based applications. The enhanced spintronic properties of TM-adsorbed SiCNTs and b-AsP open new avenues for their application in spintronic devices. The high spin polarization and induced magnetism in these materials can improve the performance of data storage technologies, magnetic sensors, and advanced computing systems. The thermal stability and tunable electronic properties of SiCNTs and b-AsP further enhance their suitability for high-performance spintronic applications. The application of spintronic devices using a standard mCell has also been proposed to show how spintronic technology coexists with conventional electronic circuits. A fault-tolerant Arithmetic Logic Unit (ALU) has been proposed and simulated. Magnetic cell (mCell)-based logic is an efficient approach for the construction of digital circuits as it occupies less area, is non-volatile, and has negligible static power consumption. This study proposes a new design for an ALU that is made using mCell logic. Simulation results show that the proposed ALU design achieves a power delay product of 88.98 fJ through the Fout pin and 112.76 fJ through the Cout pin, which is very low compared with traditional CMOS-based designs. Future research should focus on experimental validation, further optimization of TM adsorption techniques, device integration, and exploring other two-dimensional (2D) materials with similar tunable properties to expand the scope of spintronic applications. This research contributes to the advancement of spintronics by providing insights into the potential of TM-induced high spin polarization in SiCNTs and b-AsP, paving the way for the development of next-generation spintronic devices.