Unlike most materials that are either insulators or conductors, topological insulators are both. They are insulators inside but conduct electricity via their surface. Since electrons on their surface are extremely mobile and also carry magnetic moment, this emerging class of materials might make spintronic components possible. Specifically, spintronic components would not be based on the movement of charge carriers like electrons as in semiconductor components, but on the manipulation of their spins. An EU-funded team of physicists worked on how the spins of electrons in topological insulators can be controlled. In the framework of the STIFNANO (Spintronics with topological insulator/ferromagnet nanodevices) project, they installed a dual-chamber molecular beam epitaxial (MBE) system at the Catalan Institute of Nanoscience and Nanotechnology (ICN2) in Spain. The MBE system for the growth of ultra-high-purity epitaxial thin films is one of a few in Europe. Physicists used this unique facility to grow topological insulators with well-defined composition and thickness. New procedures were also developed for growing different bismuth-based topological insulators. One of the main achievements of STIFNANO was the complete suppression of defects in single-crystalline thin films for topological insulators. Extended crystal defects are commonly observed in these materials and are detrimental to the observation of surface-related phenomena. In addition, physicists developed the experimental set-up to study topological insulator/ferromagnet heterostructures. Generating spin-charge exchange-induced ferromagnetism on their interface provides an innovative approach to realising devices exhibiting quantum functionalities. The STIFNANO experimental system has already been exploited to collect the first-ever current-induced ferromagnetic resonance measurements. The enhanced interfacial magnetism measured can be very relevant to building new spintronic devices able to perform calculations using the laws of quantum mechanics.
Topological insulators, spintronics, STIFNANO, ferromagnet, thin films