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, CEA DAM Île-de-France
Citations	14
Analysis	Full AI Review Included

Executive Summary

Core Innovation: Successful integration of wide-field Nitrogen-Vacancy (NV) diamond magnetic microscopy with Synchrotron X-ray Diffraction (XRD) for simultaneous, in situ measurements under high pressure using a Diamond Anvil Cell (DAC).
Sensor Design: Ensemble NV centers were engineered directly onto the culet of one diamond anvil, acting as a quantum sensor layer for magnetic field mapping.
Proof-of-Principle: The technique was validated by tracking the high-pressure phase transition in iron (Fe) at 300 K.
Correlated Results: The structural transition (body-centered-cubic α-Fe to hexagonal close-packed ε-Fe) and the magnetic transition (ferromagnetic to non-magnetic) were confirmed to occur within a similar pressure range (12.2 GPa to 20.0 GPa).
Methodology: A compact, portable NV optical setup was designed to be slid on and off the XRD bench, allowing alternating magnetic and structural measurements at each pressure step.
Future Capability: This combined scheme is well-suited to complement fourth-generation synchrotrons, enabling observation of dynamic, electronic, and structural properties with spatial resolution potentially down to 100 nm.

Technical Specifications

Parameter	Value	Unit	Context
Maximum Pressure Achieved	32.7	GPa	Highest pressure reached during the experimental run.
Iron Phase Transition Range (α→ε)	12.2 to 20.0	GPa	Pressure range where both phases coexist and magnetic field decreases.
X-ray Wavelength	0.3738	A	Monochromatic X-ray beam used at the PSICHÉ beamline.
X-ray Beam Spot Diameter	~80	µm	Diameter of the X-ray beam available during the experiment.
Pinhole Diameter (PH)	50	µm	Used to limit the X-ray beam size and prevent parasitic diffraction from the gasket.
NV Center Implantation Depth	20	nm	Depth of the NV layer below the diamond anvil surface.
NV Center Concentration	~10⁴	defects/µm²	Concentration within the implanted NV layer.
Optical Pumping Wavelength	532	nm	Continuous-wave green laser used for optical pumping.
NV Spin Resonance Frequency (Zero Field)	2.87	GHz	Frequency for the m_s = 0 to m_s = ±1 transition.
Applied Bias Magnetic Field (M)	~9	mT	External field used to induce sample magnetization and split NV resonances.
Diamond Anvil Culet Diameter	300	µm	Diameter of the culets on the type IIas Almax-Boehler anvils.
Pressure Transmitting Medium	NH₃BH₃	N/A	Ammonia borane salt used for pressure transmission.

Key Methodologies

NV Sensor Preparation: Nitrogen-Vacancy (NV) centers were created via ion implantation on the culet of one diamond anvil, forming a wide-field magnetic sensor layer.
DAC Setup: A Diamond Anvil Cell (DAC) was assembled using a rhenium gasket. The sample consisted of multiple iron beads (99.5% purity) and a gold (Au) bead (pressure gauge), embedded in NH₃BH₃ pressure medium.
MW Delivery: A single copper wire loop was wrapped around the NV-doped anvil, serving as the antenna (A) for microwave (MW) excitation. A slit was cut in the gasket to ensure MW propagation and prevent eddy current screening.
Pressure Cycling and Biasing: Pressure was increased incrementally using a membrane-actuated DAC. A permanent magnet applied a constant external bias field (~9 mT) to magnetize the iron sample.
Sequential Measurement: At each pressure step, two diagnostics were performed alternately:
- NV Magnetometry: The compact optical microscope was slid onto the bench. Green laser light (532 nm) pumped the NV centers, and the red photoluminescence (PL) was collected. Optically Detected Magnetic Resonance (ODMR) spectra were recorded pixel-by-pixel by sweeping the MW frequency.
- XRD Measurement: The NV microscope was removed. The DAC was exposed to the monochromatic X-ray beam (0.3738 A, 50 µm pinhole). Diffraction patterns were recorded on an image plate detector (IPD).
Magnetic Field Extraction: The splitting value (Δc) of the selected NV family was mapped. The contribution from the external bias field and non-hydrostatic stress was removed by referencing the splitting measured 15 µm away from the sample, isolating the magnetic field (B_sample,c) generated by the iron magnetization.
Phase Correlation: The pressure dependence of the averaged B_sample,c (magnetic signal) was compared directly against the structural phase evolution determined by the XRD patterns (α-Fe, ε-Fe, and coexistence).

Commercial Applications

High-Pressure Materials Research: Simultaneous tracking of structural and magnetic transitions in novel materials (e.g., magnetic alloys, complex oxides, hydrogen storage compounds) under extreme static compression.
Geophysical Modeling: In situ characterization of iron and iron-based compounds relevant to planetary cores, providing crucial data on magnetism and phase stability under megabar pressures.
Quantum Sensor Integration: Development and validation of robust, miniaturized NV diamond quantum sensors for operation within highly constrained, high-radiation, or high-pressure environments, such as synchrotron beamlines.
Advanced Synchrotron Diagnostics: Complementing existing X-ray techniques (XRD, XMCD) by providing high-resolution vector magnetic field mapping, enabling a comprehensive understanding of material behavior (dynamic, electronic, and structural) at the nanoscale (projected resolution < 100 nm).
Spintronics and Data Storage: Quantitative measurement and modeling of magnetization texture in micrometer-sized magnetic structures under pressure, relevant for optimizing device performance and stability.

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]