Regensburg 2022 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 47: Focus Session: Atomic-Scale Studies of Spins on Surfaces with Scanning Tunneling Microscopy 1

O 47.2: Vortrag

Mittwoch, 7. September 2022, 15:30–15:45, S051

Longitudinal and transverse electron paramagnetic resonance in a scanning tunneling microscope — •Tom S. Seifert¹, Stepan Kovarik², Pietro Gambardella², and Sebastian Stepanow² — ¹FU Berlin — ²ETH Zürich

Combining scanning tunneling microscopy (STM) with electron-paramagnetic resonance (EPR) allows for sensitive probing magnetic interactions at atomic scales [1]. However, the experimental requirements for driving the EPR transitions are not obvious [2,3]. In-depth understanding of what drives EPR-STM is mandatory to explore novel material systems with high sensitivity. Here, we acquire and model EPR spectra of single Fe and hydrogenated Ti atoms on bilayer MgO on Ag using a radio frequency (RF) antenna close to the STM junction [4]. We investigate in a systematic way the impact of RF excitation strength and tunneling parameters on the EPR signal and find strong evidence for a piezoelectric coupling mechanism [5]. Specifically, transverse magnetic field gradients drive the spin-1/2 hydrogenated Ti, whereas longitudinal magnetic field gradients drive the spin-2 Fe. Finally, we demonstrate how the choice of specific tip-sample distances allows one to minimize the impact of tip magnetic fields on the EPR-STM measurements thereby excluding a major experimental uncertainty when determining single-atom magnetic moments [6].

[1] S. Baumann et al., Science 350 (2015) [2] K. Yang et al., PRL 122 (2019) [3] P. Willke et al., Nano Lett. 19 (2019) [4] T.S. Seifert et al., PRR 2 (2020) [5] T.S. Seifert et al., Sci. Adv. 6 (2020) [6] T.S. Seifert et al., PRR 3 (2021)