Electron Paramagnetic Resonance on a Tip Reveals Thickness-Dependent Spin Heterogeneity in Two-
6 affiliations
- 1Johannes Kepler University Linz, Gruberstraße 40, Linz, 4020
- 2Instituto de Ciencia Molecular, Universitat de València, Catedrático José Beltrán 2, Paterna, Spain, 46980
- 3Università degli Studi di Firenze, Via della Lastruccia, 3, Sesto Fiorentino, Italy, 50019
- 4School of Chemistry
- 5University of Birmingham
- 6Diamond Light Source, Electron Physical Science Imaging Centre, OX11 0DE, Didcot, UK
Abstract
Direct characterization of the spin centers that provide the magnetic states of low-dimensional magnetic materials is key to understand whether the magnetic properties arise from defects, interfaces, or surface-specific coordination environments, and how they can thus be employed in devices. The spectroscopic technique par excellence for this purpose is electron paramagnetic resonance (EPR) which has seen recent expansion to single spins but remains challenging for nanostructures on insulating surfaces. Here, we overcome this limitation and demonstrate local spin-resonance spectroscopy of nanoscale systems on insulators. We achieve this by combining EPR detection with scanning microwave microscopy (SMM) at X-band frequencies of ≈9.3 GHz, with resonant spin absorptions identified as local field-dependent microwave losses, available by mapping the complex admittance under a swept magnetic field. We demonstrate the potential of the technique on single flakes of the two-dimensional Fe–Ni Hofmann clathrate. The new technique reveals a thickness-dependent evolution from bulk-like toward low-dimensional spinresonance behavior, allowing the investigation of flakes from ≈5-15 nm to >100–200 nm thick, in conditions inaccessible to other surface EPR methods. The observed thickness-dependent response is consistent with increasing contributions from surface, interface, and undercoordinated Fe environments. These new developments allow a unique route to probe dimensional effects in magnetism, make surface effects and defects accessible in insulators, and open the possibility of directly observing EPR not just on atoms and molecules, but on single electronic nanodevices, such as Single Electron Transistors and quantum dots.
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BibTeX
@misc{fabi2026electron,
title = {{Electron Paramagnetic Resonance on a Tip Reveals Thickness-Dependent Spin Heterogeneity in Two-}},
author = {Gianluca Fabi and Ramon Torres and Maxwell Sparey and Javier Castells-Gil and Christopher S. Allen and Joaquin Soriano-Lopez and Lapo Bogani and Georg Gramse},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010070/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010070/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Electron Paramagnetic Resonance on a Tip Reveals Thickness-Dependent Spin Heterogeneity in Two-
AU - Gianluca Fabi
AU - Ramon Torres
AU - Maxwell Sparey
AU - Javier Castells-Gil
AU - Christopher S. Allen
AU - Joaquin Soriano-Lopez
AU - Lapo Bogani
AU - Georg Gramse
PY - 2026
DA - 2026/10/07
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010070/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010070/v1
AB - Direct characterization of the spin centers that provide the magnetic states of low-dimensional magnetic materials is key to understand whether the magnetic properties arise from defects, interfaces, or surface-specific coordination environments, and how they can thus be employed in devices. The spectroscopic technique par excellence for this purpose is electron paramagnetic resonance (EPR) which has seen recent expansion to single spins but remains challenging for nanostructures on insulating surfaces. Here, we overcome this limitation and demonstrate local spin-resonance spectroscopy of nanoscale systems on insulators. We achieve this by combining EPR detection with scanning microwave microscopy (SMM) at X-band frequencies of ≈9.3 GHz, with resonant spin absorptions identified as local field-dependent microwave losses, available by mapping the complex admittance under a swept magnetic field. We demonstrate the potential of the technique on single flakes of the two-dimensional Fe–Ni Hofmann clathrate. The new technique reveals a thickness-dependent evolution from bulk-like toward low-dimensional spinresonance behavior, allowing the investigation of flakes from ≈5-15 nm to >100–200 nm thick, in conditions inaccessible to other surface EPR methods. The observed thickness-dependent response is consistent with increasing contributions from surface, interface, and undercoordinated Fe environments. These new developments allow a unique route to probe dimensional effects in magnetism, make surface effects and defects accessible in insulators, and open the possibility of directly observing EPR not just on atoms and molecules, but on single electronic nanodevices, such as Single Electron Transistors and quantum dots.
ER -