Spin LEGOs - Bottom-up Fabrication of Model Magnetic Systems
Scanning tunneling microscopy (STM) has emerged as a leading tool which can address current issues in spin-related physics because of both combined high spatial and energy resolution. With the development of sub-Kelvin high-magnetic field STM, two complementary methods, namely spin-polarized scanning tunneling spectroscopy (SP-STS) and inelastic STS (ISTS), can address single spins at the atomic scale. While SP-STS reads out the projection of the impurity magnetization, ISTS detects the excitations of this magnetization as a function of an external magnetic field. They are thus the analogs of magnetometry and spin resonance measurements pushed to the single atom limit. Shedding light on atomic scale phenomena, SP-STS and ISTS have been used to measure exchange couplings between single magnetic impurities and to address the effects of magnetocrystalline anisotropy. To this end, we have made significant contributions in this field, not only in the initial development stages; we have demonstrated for the first time that it is possible to combine single atom magnetometry (SAM) with an atom-by-atom bottom-up fabrication to realize atomic-scale magnets with tailored properties. As a first such example of this, we demonstrated that it is possible to realize an all-spin based atomic logic gate comprised of coupled Fe atoms on a metallic surface; a demonstration of a fundamental nano-spintronic concept. We were also able to extend SAM techniques to characterize single spins in a semiconductor surface, a backbone material for spintronic applications, representing a significant step forward of the application of SAM toward novel systems. In this talk, I will address these novel developments and their potential application toward future understandings of spin dynamics as well as atomic-scale understandings of spin-phenomena in novel materials like topological insulators.