Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/21025
Title: Materials for spintronics: From bulk to Nano
Authors: SHEN LEI
Keywords: Spintronics, graphene, diluted magnetic semiconductors, metallic organic frameworks, sandwich molecular wires, first-principles calculations
Issue Date: 28-Jul-2010
Source: SHEN LEI (2010-07-28). Materials for spintronics: From bulk to Nano. ScholarBank@NUS Repository.
Abstract: Spin-based electronics, or spintronics, represents a new paradigm for future electronics. Its central theme is the active manipulation of the spin of electrons in materials, in addition to their charges. The potential applications and ultimate goals of spintronics are to build spin-based transistors that would replace conventional transistors in integrated logic circuits and memory devices, which are used in future spin-electronic products, such as computer-chips, television, fax machines, cell phones, and hard disks etc. Spintronics devices are even more exciting because they are eco-friendly devices which consume less energy and produce less heat. Spintronic devices promise to be smaller, faster and far more versatile than today¿s electronic devices. However, the big challenge for realizing spintronics is to find the right materials to efficiently generate spin-polarized current. In this thesis, I focused on the investigation of the physical properties of materials for spintronics and prediction of new materials using first-principles electronic structure calculation methods. Several breakthroughs have been made in predicting a new class of spintronic materials and in providing deep physical insights in the mechanism for their applications in spintronics. 3D inorganic spintronics For the first time, we proposed a new class diluted magnetic semiconductors (DMSs) which bypass the magnetic contamination of the doped magnetic elements. Collaborating with some experimental groups, we proved our predictions experimentally. Moreover, we went beyond traditional theories and proposed a whole new physical mechanism for this type of DMSs. 1D organic spintronics Based on ab initio calculations, we studied the spin-electron transport of zig-zag graphene nanoribbon-based materials and obtained some very interesting results, and some of these results were discovered for the very first time. Our study on transport properties of linear carbon-chain revealed a very interesting spin-dependent transport of linear carbon-chain on graphene electrodes. Perfect spin-filter and spin-valve effects are predicted simultaneously to hold in a single GNR-based field-effect transistor (FET). 3D metal-organic frameworks (MOFs) MOFs, consisting of inorganic metal-oxide clusters linked with organic chains, have a porous network structure. I theoretically proposed a rule for the long-range magnetic exchange coupling in Cu(II) cluster-based MOFs and their application in spintronics. My theoretical model solves a long-standing puzzle in the origin of ferromagnetism in most Cu(II) cluster-based MOFs. 1D organometallic sandwich molecular wires (SMWs) The spin transport in SMW devices is studied in this thesis. The perfect spin filter effect is found in FeCp clusters, where Cp is cyclopentadienyl. The experimental growth mechanism is also proposed based on my charge-transfer theory. Moreover, I have given a physical insight in the long-range spin-exchange coupling in bimetallic multi-decker sandwich molecular wires.
URI: http://scholarbank.nus.edu.sg/handle/10635/21025
Appears in Collections:Ph.D Theses (Open)

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