Combined synchrotron x-ray diffraction and NV diamond magnetic microscopy measurements at high pressure

At a Glance

Metadata	Details
Publication Date	2020-10-01
Journal	New Journal of Physics
Authors	Loïc Toraille, Antoine Hilberer, Thomas Plisson, Margarita Lesik, Mayeul Chipaux
Institutions	Centre National de la Recherche Scientifique, Thales (France)
Citations	14
Analysis	Full AI Review Included

Combined Synchrotron XRD and NV Diamond Magnetic Microscopy at High Pressure

Executive Summary

This technical analysis summarizes the successful integration of wide-field Nitrogen-Vacancy (NV) diamond magnetic microscopy with Synchrotron X-ray Diffraction (XRD) within a Diamond Anvil Cell (DAC) environment. This combined technique enables simultaneous measurement of structural and magnetic properties under extreme pressure, opening new avenues for solid-state physics research.

Core Achievement: Simultaneous, non-perturbing measurement of structural (XRD) and magnetic (NV-ODMR) transitions in iron samples compressed up to 32.7 GPa.
Key Material: Specifically engineered Single Crystal Diamond (SCD) anvils featuring a shallow, high-density NV layer (10⁴ defects/µm² at 20 nm depth) on the culet surface.
Application Demonstrated: Tracking the correlated $\alpha$-Fe (ferromagnetic, bcc) to $\epsilon$-Fe (non-magnetic, hcp) phase transition, which occurred between 12.2 GPa and 20.0 GPa at 300 K.
Methodology: Optically Detected Magnetic Resonance (ODMR) was used to map the stray magnetic field created by the sample magnetization, validating NV diamond as a robust quantum sensor in high-pressure environments.
Compatibility: The NV microscope setup was designed to be compact and portable, allowing it to be slid on and off the XRD bench, ensuring compatibility with synchrotron beamlines (e.g., SOLEIL PSICHÉ).
Future Potential: This work paves the way for high-resolution studies (down to 100 nm spatial resolution) of dynamic, electronic, and structural properties using next-generation synchrotron sources.

Technical Specifications

The following hard data points were extracted from the experimental results and setup description:

Parameter	Value	Unit	Context
Maximum Pressure Achieved	32.7	GPa	Upper limit of the progressive pressure increase
Operating Temperature	300	K	Room temperature experiment
Diamond Anvil Culet Diameter	300	µm	Size of the Type IIa Almax-Boehler anvils
NV Center Density (Implanted)	10⁴	defects/µm²	Concentration of NV centers in the sensing layer
NV Layer Depth	20	nm	Distance below the diamond surface
ODMR Zero-Field Resonance	2.87	GHz	NV center spin resonance frequency
Applied Bias Magnetic Field	9	mT	Used to induce magnetization and split ODMR resonances
X-ray Wavelength ($\lambda$)	0.3738	Å	Monochromatic beam used for XRD
X-ray Pinhole Diameter	50	µm	Used to limit beam size and avoid gasket diffraction
$\alpha$-Fe $\rightarrow$ $\epsilon$-Fe Transition Start	12.2 - 13.8	GPa	Pressure range where $\epsilon$-Fe phase first appears
$\alpha$-Fe $\rightarrow$ $\epsilon$-Fe Transition End	20.0	GPa	Pressure where the $\alpha$-Fe phase completely disappears
Magnetic Field Sensitivity (Sample)	Few hundreds	µT	Magnetic field detected above the $\alpha$-Fe samples

Key Methodologies

The experiment successfully combined high-pressure generation, quantum sensing, and synchrotron analysis through precise material engineering and setup design:

Diamond Anvil Engineering: Single Crystal Diamond (SCD) anvils were specifically engineered. A layer of NV centers was created on the culet tip via nitrogen ion implantation, resulting in a high-density layer (10⁴ defects/µm²) located 20 nm below the surface.
DAC Sample Preparation: Iron beads (99.5% purity) and a gold pressure gauge bead (5 µm diameter) were loaded into a Rhenium gasket, using NH₃BH₃ as the solid-state pressure transmitting medium.
Microwave (MW) Excitation: A single loop of insulated copper wire was wrapped around the NV-doped anvil to serve as the antenna for the 2.87 GHz MW excitation. A slit was cut into the metallic Rhenium gasket to prevent MW screening.
Optical Pumping and Detection: NV centers were optically pumped using a continuous-wave 532 nm green laser. The resulting red photoluminescence (PL) was collected via a $\times 40$ objective (NA 0.4) and imaged onto a CMOS camera.
Alternating Measurements: The compact NV magnetic microscope was mounted on a sliding stage, allowing researchers to rapidly alternate between magnetic field mapping (ODMR) and structural analysis (XRD) at each pressure step without disturbing the DAC.
Data Processing: The ODMR splitting ($\Delta$c) maps were analyzed. To isolate the magnetic field generated by the iron sample (B_sample,c) from external bias and non-hydrostatic stress effects, a reference splitting value was measured 15 µm away from the sample and subtracted.

6CCVD Solutions & Capabilities

6CCVD is uniquely positioned to supply the advanced MPCVD diamond materials and engineering services required to replicate and extend this groundbreaking research in high-pressure quantum sensing. The success of this experiment hinges on the quality and precise engineering of the SCD anvil, which is a core competency of 6CCVD.

Research Requirement	6CCVD Solution & Capability	Value Proposition
High-Purity SCD Anvils	Optical Grade SCD: SCD plates up to 500 µm thick, featuring ultra-low nitrogen content for minimal background fluorescence and high optical transmission (required for 532 nm pumping).	Ensures maximum PL collection efficiency and low birefringence for clear optical access through the anvil.
Custom Geometry & Size	Custom Dimensions: We supply SCD plates and wafers up to 125 mm (PCD) and custom-cut SCD pieces tailored for specific DAC geometries (e.g., 300 µm culets or larger anvils).	Enables rapid prototyping and scaling of high-pressure cell designs beyond standard commercial sizes.
NV Layer Integration	NV Precursors & Post-Processing: We provide high-purity SCD optimized for post-growth NV creation via ion implantation (as used in this paper). We also offer in-situ nitrogen doping for bulk NV ensembles.	Guarantees precise control over the starting material properties necessary for achieving the required 10⁴ defects/µm² density and shallow depth (20 nm).
Surface Quality	Precision Polishing (Ra < 1 nm): Our SCD material is polished to an atomic-scale finish (Ra < 1 nm).	Critical for optimal optical coupling (NA 0.4 objective) and ensuring the integrity of the shallow 20 nm implanted layer.
Integrated MW Structures	Custom Metalization: Internal capability for depositing thin films (Au, Pt, Pd, Ti, W, Cu) directly onto the diamond surface.	Allows for the integration of microwave transmission lines or electrodes directly onto the anvil culet, eliminating the need for external copper loops and improving MW efficiency.
Engineering Support	In-House PhD Team: 6CCVD provides expert consultation on material selection, doping strategies (BDD, N-doping), and surface preparation for high-pressure magnetometry and quantum sensing projects.	Accelerates R&D cycles by ensuring the diamond material is perfectly matched to the extreme conditions and quantum requirements of the experiment.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Abstract We report the possibility to simultaneously perform wide-field nitrogen-vacancy (NV) diamond magnetic microscopy and synchrotron x-ray diffraction measurements at high pressure. NV color centers are created on the culet of a diamond anvil which is integrated in a diamond anvil cell for static compression of the sample. The optically detected spin resonance of the NV centers is used to map the stray magnetic field produced by the sample magnetization. Using this combined scheme, the magnetic and structural behaviors can be simultaneously measured. As a proof-of-principle, we record the correlated α -Fe to ε -Fe structural and magnetic transitions of iron that occur here between 15 and 20 GPa at 300 K.

Tech Support

Original Source

DOI: https://doi.org/10.1088/1367-2630/abc28f

References

2018 - Solids, liquids, and gases under high pressure [Crossref]
2017 - High-pressure studies with x-rays using diamond anvil cells [Crossref]
2016 - High pressure XAS, XMCD and IXS [Crossref]
2019 - Principles and techniques of the quantum diamond microscope [Crossref]
2018 - Screening and engineering of colour centres in diamond [Crossref]
2013 - The nitrogen-vacancy colour centre in diamond [Crossref]
2008 - High-sensitivity diamond magnetometer with nanoscale resolution [Crossref]
2009 - Influence of a static magnetic field on the photoluminescence of an ensemble of nitrogen-vacancy color centers in a diamond single-crystal [Crossref]
2015 - Magnetic imaging with an ensemble of nitrogen-vacancy centers in diamond [Crossref]