Enhancement of magnetic detection by ensemble NV color center based on magnetic flux concentration effect
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-01-01 |
| Journal | Acta Physica Sinica |
| Authors | Zhonghao Li, Tianyu Wang, Qi Guo, Hao Guo, Huanfei Wen |
| Citations | 5 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research details the successful integration of a Magnetic Flux Concentrator (MFC) with an ensemble Nitrogen-Vacancy (NV) diamond sensor to significantly enhance magnetic detection sensitivity using Continuous Wave Optical Detection Magnetic Resonance (CW-ODMR) imaging.
- Core Value Proposition: Achieved effective enhancement of weak magnetic field detection sensitivity at room temperature by leveraging the magnetic flux concentration effect of a passive Permalloy structure.
- Sensitivity Improvement: The system demonstrated a measured improvement in magnetic sensitivity from a baseline of 1.10 nT/Hz1/2 (without MFC) to 0.30 nT/Hz1/2 (with a 1.0 mm MFC gap).
- Enhancement Factor: A magnetic field enhancement factor (N) of 10.35 was experimentally verified for the 1.0 mm MFC gap, closely matching simulation results (10.67).
- Optimal Performance Prediction: Based on fitting experimental data and simulation models, the optimal performance is estimated to reach an enhancement factor of 18.21 and a sensitivity of 0.25 nT/Hz1/2 at a 0.5 mm MFC gap.
- Methodology: The enhancement was validated using a wide-field CW-ODMR imaging system, allowing for spatial mapping of the enhanced magnetic field distribution.
- Sensor Material: The sensor utilized a high-concentration ensemble NV diamond (3 ppm) grown on the (100) face.
- Application Focus: The results provide a crucial reference for developing high-precision quantum measurement technology for weak and extremely weak magnetic field applications.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Initial Magnetic Sensitivity (No MFC) | 1.10 | nT/Hz1/2 | Baseline CW-ODMR measurement. |
| Measured Sensitivity (1.0 mm MFC Gap) | 0.30 | nT/Hz1/2 | Achieved sensitivity with MFC integration. |
| Estimated Optimal Sensitivity (0.5 mm MFC Gap) | 0.25 | nT/Hz1/2 | Predicted best-case performance based on fitting. |
| Measured Enhancement Factor (N) | 10.35 | Dimensionless | At 1.0 mm MFC gap width. |
| Estimated Enhancement Factor (N) | 18.21 | Dimensionless | Predicted at 0.5 mm MFC gap width. |
| NV Diamond Dimensions | 1.0 x 4.0 x 0.5 | mm | Ensemble NV sample size (Element Six). |
| NV Concentration | ~3 | ppm | Nitrogen-Vacancy center concentration. |
| Excitation Wavelength | 532 | nm | Green laser source power (100 mW). |
| Microwave Frequency Range | 2.7 - 3.0 | GHz | CW-ODMR sweep range. |
| Microwave Step Size | 0.15 | MHz | Frequency step resolution. |
| MFC Material | 1J79 | Permalloy | High magnetic permeability soft magnetic material. |
| MFC Relative Permeability (Simulation) | 10000 | Dimensionless | Used in COMSOL modeling. |
| System Spatial Resolution | ~1 | ”m/pixel | Achieved after 4x4 pixel averaging. |
| Data Acquisition Time (Full Scan) | 80 | s | Time for one 2000-step ODMR imaging cycle. |
Key Methodologies
Section titled âKey MethodologiesâThe experiment involved integrating a custom Magnetic Flux Concentrator (MFC) with a diamond NV sensor and validating the enhancement using a wide-field CW-ODMR imaging setup.
- Sensor Selection: Utilized a high-concentration ensemble NV diamond (3 ppm, 1.0 x 4.0 x 0.5 mm) grown on the (100) crystal face.
- MFC Design and Modeling: Designed paired T-shaped flake MFC structures using 1J79 Permalloy. COMSOL software was used to simulate the magnetic flux concentration effect, setting the materialâs relative magnetic permeability to 10000.
- System Setup: Constructed a wide-field magnetic imaging system comprising:
- Optical System: 532 nm green laser, beam expander, dichroic mirror, 20x/0.4 objective lens, and a camera (CS2100M-USB) for fluorescence imaging.
- Microwave System: Microwave source (SMA 100A) providing 30 dBm power via a microwave antenna (2.7-3.0 GHz sweep).
- Magnetic System: A pair of cylindrical permanent magnets (Ă40 x 10 mm) in a near-Helmholtz configuration to generate the static magnetic field.
- MFC Integration and Adjustment: The paired MFCs were placed symmetrically on either side of the diamond sample along the spatial axis. A precision adjustment mechanism allowed the MFC gap width to be varied (tested from 1.0 mm up to 10.0 mm).
- Data Acquisition (CW-ODMR): Performed synchronized sweeping of the microwave frequency and camera exposure (5 ms exposure time, 2000 steps per scan) to acquire 3D fluorescence data (X, Y, Frequency).
- Magnetic Field Mapping: The acquired 3D data was processed to extract the ODMR curve for each pixel. The magnetic field (Bn) was calculated from the difference in the resonance peak frequencies (Îx) using the Zeeman splitting formula.
- Enhancement Factor Measurement: The magnetic enhancement factor (N) was determined by measuring the magnetic field at the center of the MFC gap (Bm) and dividing it by the baseline field measured without the MFC (Bj), i.e., N = Bm/Bj.
- Sensitivity Calculation: Magnetic sensitivity (η) was calculated using the measured enhancement factor (N), the ODMR contrast (C), and the photon collection rate (R).
Commercial Applications
Section titled âCommercial ApplicationsâThe enhanced NV magnetometry system is highly relevant for applications requiring high-sensitivity, room-temperature magnetic field detection and imaging.
- Biomagnetism:
- High-resolution detection of weak magnetic signals from biological samples (e.g., neural activity, cellular processes).
- Development of compact, non-invasive room-temperature sensors for Magnetoencephalography (MEG) or Magnetocardiography (MCG).
- Materials Science and Nondestructive Testing (NDT):
- Mapping weak magnetic fields generated by defects, stress, or current flow in micro- and nano-scale electronic components.
- High-resolution imaging of magnetic domains and structures in novel magnetic materials.
- Geophysics and Environmental Sensing:
- Precision measurement of weak static magnetic fields for geological surveys and resource exploration.
- Portable, high-sensitivity magnetometers for environmental monitoring (e.g., detecting magnetic contaminants).
- Quantum Information Science:
- Serving as a key component in advanced quantum nodes and hybrid quantum systems (as referenced in the related articles, e.g., entanglement with superconducting circuits).
- Precision Metrology:
- Calibration and testing of other magnetic sensors, leveraging the NV centerâs stable, quantum-based reference.
View Original Abstract
The high-sensitivity magnetic sensor is the key to the weak magnetic and extremely weak magnetic detection imaging. In this paper, based on ensemble nitrogen-vacancy (NV) color center in diamond, a wide-field magnetic field distribution imaging system combined with the magnetic flux concentrator (MFC) is built for enhancing the magnetic detection. The paired T-shape chip MFC structures are designed and prepared based on the simulation of magnetic flux concentration effect, and the enhancement of magnetic field of MFC is verified by continuous wave optical detection magnetic resonance (CW-ODMR) imaging technology. When the gap width between the MFCs is 1.0 mm, the magnetic enhancement factor is about 10.35. To verify the effectiveness of the magnetic enhancement effect of the MFC, The magnetic enhancement effects are also measured under different magnetic field strengths and different gap widths. The magnetic sensitivity of the system increases from 1.10 nT/Hz<sup>1/2</sup> to 0.30 nT/Hz<sup>1/2</sup>. By comparing the simulations with the measurements, the relationship between the measured magnetic enhancement multiple and the gap width can be obtained, and the better magnetic enhancement capability and sensitivity of the experimental system are also estimated. When the MFCâs gap width is 0.5 mm, the corresponding magnetic enhancement factor is increased to 18.21, and the corresponding magnetic sensitivity is 0.25 nT/Hz<sup>1/2</sup>. These results show that the magnetic detection sensitivity of the ensemble NV in diamond can be effectively improved based on magnetic flux concentration effect, which provides a reference for the applications of precision quantum measurement technology in weak magnetic and extremely weak magnetic detection.