Imaging magnetic transition of magnetite to megabar pressures using quantum sensors in diamond anvil cell
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2024-10-14 |
| Journal | Nature Communications |
| Authors | Mengqi Wang, Yu Wang, Zhixian Liu, Ganyu Xu, Bo Yang |
| Institutions | Carnegie Institution for Science, University of Science and Technology of China |
| Citations | 15 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled āExecutive SummaryāThis research successfully developed and demonstrated a highly sensitive quantum sensing technique using Nitrogen-Vacancy (NV) centers within a Diamond Anvil Cell (DAC) to measure magnetic properties at megabar pressures.
- Megabar Magnetic Sensing: The technique breaks the pressure limitation on quantum sensors, enabling in-situ magnetic detection up to 130 GPa (megabar range).
- Stress Modulation Innovation: Performance degradation due to non-hydrostatic stress was overcome by modulating the uniaxial stress component (Ļā„) along the NV axis, specifically utilizing a (111)-cut diamond anvil.
- High Performance: The optimized sensor achieved a magnetic detection sensitivity of approximately 1 ĀµT/āHz and sub-microscale spatial resolution, suitable for imaging nanoscale single-domain grains.
- Fe3O4 Transition Mapped: The method was used to directly image and characterize the macroscopic magnetic transition of magnetite (Fe3O4) under pressure.
- Observed Transitions: Fe3O4 transitioned from ferrimagnetic (Ī±-Fe3O4) to weak ferromagnetic (Ī²-Fe3O4), and finally to paramagnetic (Ī³-Fe3O4) above 70 GPa.
- Engineering Relevance: This methodology provides a new tool for quantitatively analyzing macroscopic magnetism and local magnetic evolution in materials under extreme conditions, crucial for fields like high-temperature superconductivity research.
Technical Specifications
Section titled āTechnical Specificationsā| Parameter | Value | Unit | Context |
|---|---|---|---|
| Maximum Pressure Achieved | 130 | GPa | Demonstrated operational limit of NV sensor. |
| Magnetic Sensitivity (Optimized) | ~1 | ĀµT/āHz | Achieved at megabar pressures (130 GPa). |
| Spatial Resolution | Sub-microscale | Āµm | Estimated from optical diffraction limit. |
| ODMR Contrast Enhancement | ~30 | % | Observed contrast for optimized NV centers at 130 GPa. |
| ODMR Linewidth (Ī) | ~20 | MHz | Narrowed linewidth achieved at 128.6 GPa. |
| NV Center Implantation Depth | ~9 | nm | Distance of NV layer from the diamond surface. |
| Implantation Ion | 14N+ | - | Used for creating NV centers. |
| Implantation Energy | 6 | keV | Used for 14N+ ion implantation. |
| Implantation Dose | 1 x 1013 | /cm2 | Dose used for 14N+ ion implantation. |
| Magnetite PM Transition Pressure | >70 | GPa | Observed transition pressure for Ī³-Fe3O4. |
| NV Center Zero-Field Splitting (D0) | 2.87 | GHz | Ambient condition value. |
Key Methodologies
Section titled āKey MethodologiesāThe experiment relied on integrating optimized NV quantum sensors directly into a Diamond Anvil Cell (DAC) setup to perform Optically Detected Magnetic Resonance (ODMR) measurements under extreme pressure.
- DAC Setup: A BeCu symmetric DAC with a Rhenium gasket was used to create the high-pressure environment.
- Diamond Anvil Preparation: HPHT type-IIa (Non-fluorescent) single crystal diamonds were used. The anvils were specifically (111)-cut to minimize the perpendicular uniaxial stress component (Ļā„) on the [111] NV centers, thereby preserving high ODMR contrast and narrow linewidth.
- NV Center Fabrication: A shallow layer of NV centers (~9 nm deep) was created via low-energy (6 keV) 14N+ ion implantation (Dose: 1 x 1013/cm2), followed by vacuum annealing (1000 Ā°C, ~2 h).
- Sample Preparation: A small single crystal magnetite (Fe3O4) sample (~4 Āµm x 5 Āµm x 1 Āµm) was placed on the diamond culet surface, near the NV layer.
- Pressure Medium and Microwave: KCl (Potassium Chloride) was used as the pressure-transmitting medium (PTM) for a quasi-hydrostatic environment. A Platinum (Pt) wire, compressed between the gasket and anvil pavilion facets, served as the microwave radiation guide.
- Optical Readout and Initialization: A 532 nm laser was used for optical initialization and readout of the NV center spin state.
- Pressure Calibration: Ruby fluorescence was used for calibration below 20 GPa, and diamond edge Raman spectroscopy was used for calibration above 20 GPa.
Commercial Applications
Section titled āCommercial ApplicationsāThe development of robust, high-sensitivity quantum sensors capable of operating under megabar pressures opens new avenues for materials engineering and fundamental physics research.
- High-Pressure Materials Characterization: Direct, in-situ measurement and imaging of magnetic microstructures (domains, stray fields) in bulk materials synthesized or studied under extreme conditions.
- Superconductivity Research: Direct detection of the Meissner effect (magnetic expulsion) in high-temperature superconducting hydrides (e.g., CeH9, LuHxNy) under megabar pressures, resolving controversies regarding their existence and properties.
- Quantum Sensing and Metrology: Advancing the operational range of NV center magnetometers for use in harsh environments, potentially leading to new standards for pressure-dependent magnetic metrology.
- Geophysics and Planetary Science: Studying the magnetic evolution and spin transitions of key minerals (like magnetite) under pressures mimicking Earthās core and mantle conditions.
- Advanced Sensor Design: Providing critical data on stress-induced spin crossover effects, informing the design of next-generation quantum sensors optimized for high-stress or non-hydrostatic environments.
View Original Abstract
Abstract High-pressure diamond anvil cells have been widely used to create novel states of matter. Nevertheless, the lack of universal in-situ magnetic measurement techniques at megabar pressures makes it difficult to understand the underlying physics of materialsā behavior at extreme conditions, such as high-temperature superconductivity of hydrides and the formation or destruction of the local magnetic moments in magnetic systems. Here, we break through the limitations of pressure on quantum sensors by modulating the uniaxial stress along the nitrogen-vacancy axis and develop the in-situ magnetic detection technique at megabar pressures with high sensitivity ( $$\sim 1{{{\rm{\mu }}}}{{{\rm{T}}}}/\sqrt{{{{\rm{Hz}}}}}$$ <mml:math xmlns:mml=āhttp://www.w3.org/1998/Math/MathMLā> <mml:mo>~</mml:mo> <mml:mn>1</mml:mn> <mml:mi>Ī¼</mml:mi> <mml:mi>T</mml:mi> <mml:mo>/</mml:mo> <mml:msqrt> <mml:mrow> <mml:mi>Hz</mml:mi> </mml:mrow> </mml:msqrt> </mml:math> ) and sub-microscale spatial resolution. By directly imaging the magnetic field and the evolution of magnetic domains, we observe the macroscopic magnetic transition of Fe 3 O 4 in the megabar pressure range from ferrimagnetic ( Ī± -Fe 3 O 4 ) to weak ferromagnetic ( Ī² -Fe 3 O 4 ) and finally to paramagnetic ( Ī³ -Fe 3 O 4 ). The scenarios for magnetic changes in Fe 3 O 4 characterized here shed light on the direct magnetic microstructure observation in bulk materials at high pressure and contribute to understanding magnetism evolution in the presence of numerous complex factors such as spin crossover, altered magnetic interactions and structural phase transitions.