Controlling spins in nanodevices via spin-orbit interaction, magnons and heat

Today’s world is driven by digital computing and information technology, which has been made possible by the mass production of integrated circuits with faster and smaller transistors. Since the last five decades, the semiconductor industry has been successful in doubling the processing power of a computer chip every 2 years. This has been achieved by making tinier transistors and packing more of them in the same chip. Presently, the transistor sizes are in the order of a few nanometres, approaching the size of atoms (a million times smaller than the diameter of a human hair). However, as the transistor size is reduced further, its performance is adversely affected due to quantum mechanical effects. This has led to the development of alternative technologies for future device applications.
This thesis is about one such alternative technology, which utilizes a fundamental property of the electron, known as ‘spin’, instead of the electronic charge. Spintronics, or spin-based electronics, can be utilized to make cheaper, faster and energy-efficient devices. The three main challenges in spintronics are the efficient generation, manipulation and detection of spin currents. The experiments presented in this thesis attempt to provide innovative solutions and investigate new ways of tackling these main challenges. Spin transport in a non-local geometry is the primary tool that has been used for this research. The experimental chapters investigate different techniques through which spins can be efficiently controlled, viz. spin-orbit interaction, heat, curved geometry and magnons. These results have direct implications for spin-based memory and logic devices.