Spin resonance amplitude and frequency of a single atom on a surface in a vector magnetic field
NOVEMBER 8, 2021
Jinkyung Kim, Won-jun Jang, Thi Hong Bui, Deung-Jang Choi, Christoph Wolf, Fernando Delgado, Yi Chen, Denis Krylov, Soonhyeong Lee, Sangwon Yoon, Christopher P. Lutz, Andreas J. Heinrich, and Yujeong Bae
Phys. Rev. B 104, 174408 (2021)
Description
Having a well-characterized spin center with scanning probes allows us to address the local environment, such as nearby magnetic atoms, defects, and local magnetic fields, at the atomic scale. We employed spin-1/2 hydrogenated titanium (Ti) atoms on MgO as a spin sensor in the scanning tunneling microscopy (STM) incorporated with electron spin resonance (ESR) technique and vector magnets. By placing the Ti sensor in the tunnel junction and rotating the external magnetic fields, we characterized the angle dependence of tip-induced magnetic fields. Moreover, for the Ti atoms at the lower symmetry site on the MgO surface, we observed the anisotropy of g-values in all three spatial directions, which is attributed to the effects of crystal fields through the spin-orbit coupling as quantified using the magnetic multiplet calculations. Our results show the ability of single atomic spins as a sensor to probe magnetic surroundings and highlight the precision of ESR-STM to identify the single atom’s spin states in a solid-state environment.
Abstract
We investigated spin-1/2 hydrogenated titanium (Ti) atoms on MgO using scanning tunneling microscopy (STM) combined with electron spin resonance (ESR) in vector magnetic fields. Rotating external magnetic fields, we observed rather drastic changes in both amplitude and frequency of resonance signals for single Ti atoms. While the variation of ESR amplitudes reflects the effects of the spin polarization of a magnetic tip and local magnetic fields created by the interaction between the tip and Ti, the change of resonance frequencies shows the anisotropy of g values for Ti atoms. Using the Ti atoms at the low-symmetry bridge adsorption site of the MgO lattice allowed for identifying the g values in all three spatial directions. Multiplet calculations confirmed the origin of this anisotropy as the spin-orbit coupling induced effects of crystal. Our results show the capability of single atomic spins as a sensor to probe magnetic surroundings and highlight the precision of ESR-STM to identify the single atom's spin states in a solid-state environment.