Transport in Magnetic and Superconducting Heterostructures

Abstract

In essence, spintronics aims to utilize the spins of electrons to store and process information, either as a supplement to or as a replacement for electron charges. Electron spins are particularly suitable for use in information technology because they are binary in nature. Some spintronics applications are already commercially available and have led to a revolution in magnetic storage technology, for instance, with the invention of the hard disk drive. Several other spintronics applications are either close to commercialization or still in the idea phase. An ambitious long-term goal of spintronics research is to trigger a revolution in low-power information and communication technologies to facilitate a more energy-efficient society.

The research in this thesis concerns two spintronic subfields: spin insulatronics and superconducting spintronics. In spin insulatronics, information is sent through magnetic insulators via spin waves. Information is sent without accompanying charge transport and thereby has the potential to significantly reduce Joule heating, the major source of energy waste in conventional electronics. Junctions consisting of superconducting and magnetic materials are of significant importance in superconducting spintronics. Close to the interfaces of such junctions, the superconductor and magnet influence each other, which can lead to the emergence of new physical phenomena. In these superconducting heterostructures, the electron spin, charge, and superconducting phase coherence can work together to increase the energy efficiency, performance, and durability of novel state-of-the-art technologies.

This thesis represents my humble contribution to spintronics and perhaps provides a modest step towards a better understanding of spin and superconducting transport via magnetic materials. Three research papers form the backbone of this thesis and investigate different aspects of spin insulatronics and superconducting spintronics. Concretely, paper 1 elucidates the role of disorder on spin-wave transport, while paper 2 and paper 3 investigate local and nonlocal transport in antiferromagnet-superconductor junctions. The main text in this thesis introduces the necessary physics for understanding the papers and attempts to set the research in a scientific perspective.