Tuning the Exchange Bias on a Single Atom from 1 mT to 10 T
Kai Yang, William Paul, Fabian D. Natterer, Jose L. Lado, Yujeong Bae, Philip Willke, Taeyoung Choi, Alejandro Ferrón, Joaquín Fernández-Rossier, Andreas J. Heinrich, and Christopher P. Lutz
Physical Review Letters 122, 227203 (2019)
As the integrated circuits continue to shrink, the spin-based devices are intensively receiving the research focuses due to their advantages, such as the fast operation and low-power consumption compared to the electronic devices. To operate the spintronic devices at the nanoscale, the localized control of magnetic moments of individual atoms or atomic clusters is required. At these scales, a versatile way to control the spin quantization axis is to apply the exchange bias at the single-atom level. In this paper, published in Phys Rev Lett., we present a technique to control the exchange bias applied to a single atom on a surface over four orders of magnitude. The exchange interaction is continuously tunable from milli-eV to micro-eV by adjusting the separation between the spin-1/2 atom on the surface and the magnetic tip of a scanning tunneling microscope (STM). Here, combining the two spectroscopic techniques, inelastic electron tunneling spectroscopy (IETS) and electron spin resonance (ESR), enables us to map out the exchange interaction over a wide span of energies. In addition, we show that a time-varying exchange interaction provides a localized AC magnetic field that resonantly drives the surface spin. The static and dynamic control of the exchange interaction at the atomic-scale provides a route towards tailored spin-based devices and materials.