William J. Cull | Searcharxiv

arXiv2026

Quantum Sensing for Spatial Spin Noise Mapping via Nitrogen-Vacancy Magnetic Quenching in Diamond

Detecting and mapping spin noise can reveal spatial variations in surface defect states, catalytic residues, free radicals, and spintronic materials. However, bulk measurements average over spatial heterogeneity, while scanning-probe maps require sequential rastering. Here, we demonstrate a microwave-free magnetic quenching (MQ) method for wide-field spin-noise mapping using nitrogen-vacancy (NV) centres in diamond. The protocol combines continuous LED illumination with a low-frequency, amplitude-modulated magnetic field, avoiding resonant microwave delivery or pulsed optical hardware. Field-induced spin-state mixing reduces NV photoluminescence, providing the primary contrast mechanism. We examine the response as a function of optical power and magnetic modulation amplitude, interpreting the results using a spin-state mixing model. The method is validated with aqueous gadobutrol concentration series, showing trends consistent with optically detected magnetic resonance (ODMR) measurements. We map spin-noise variations across boron nitride and single-walled carbon nanotube samples with differing defect and metallic catalyst contributions, supported by electron microscopy and spectroscopy. Notably, MQ detects a spin-noise response in boron nitride nanotubes that is silent in bulk EPR spectroscopy. This approach provides a practical framework for spatially resolved spin-noise sensing across quantum technologies and advanced functional materials.

physics.app-ph↗

arXiv2026

Practical Crystallography with a Transmission Electron Microscope

Three-dimensional electron diffraction (3DED) is a powerful technique providing for crystal structure solutions of sub-micron sized crystals too small for structure determination via X-ray techniques. The entry requirement, however, of a transmission electron microscope (TEM) adapted with bespoke software for coordinated sample stage rotation and continuous electron diffraction data acquisition has generally inhibited the wider uptake of 3DED. To address this limitation, we present novel software GiveMeED appropriate for controlled 3DED data acquisition. The collection of useable reflections beyond 0.8 Å makes 3DED crystallographic processing effectively routine, using standard software and workflows derived from single-crystal X-ray diffraction (SCXRD) techniques. A full experimental workflow for 3DED on a conventional TEM is described in practical terms, in combination with direct imaging, and energy dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS), for the return of comprehensive correlative descriptions of crystal morphologies and sample compositions, with due regard for the quantification of electron flux at each stage of the characterisation process. The accuracy and effectiveness of GiveMeED is demonstrated through structure solutions for case study paracetamol, copper(II) phthalocyanine, and percholorocoronene samples, characterised in their near-native states under controlled low dose conditions at either room or cryogenic temperatures, with determined unit cell parameters and atomic connectivity matching accepted literature X-ray structures for these compounds. To promote the wider adoption of 3DED, we make GiveMeED freely available for use and modification, in support of greater uptake and utilisation of structure solution procedures via electron diffraction.

cond-mat.mtrl-sci↗