Spin Resonance Amplitude and Frequency of a Single Atom on a Surface in a Vector Magnetic Field

TL;DR

This study employs ESR-STM to investigate the spin properties of a single hydrogenated Ti atom on MgO, revealing anisotropic g-values and the influence of magnetic field orientation on ESR signals, demonstrating precise single-atom spin detection.

Contribution

The paper introduces a novel application of ESR-STM to measure and analyze the anisotropic spin properties of a single atom on a surface in vector magnetic fields.

Findings

Strongly anisotropic g-values in all three spatial directions.

ESR signal amplitude and lineshape depend on magnetic field angle.

Ti spin aligns with the magnetic field, tip spin follows its anisotropy.

Abstract

We used electron spin resonance (ESR) combined with scanning tunneling microscopy (STM) to measure hydrogenated Ti (spin-1/2) atoms at low-symmetry binding sites on MgO in vector magnetic fields. We found strongly anisotropic g-values in all three spatial directions. Interestingly, the amplitude and lineshape of the ESR signals are also strongly dependent on the angle of the field. We conclude that the Ti spin is aligned along the magnetic field, while the tip spin follows its strong magnetic anisotropy. Our results show the interplay between the tip and surface spins in determining the ESR signals and highlight the precision of ESR-STM to identify the single atom's spin states.