Enhancement of magnetic detection by ensemble NV color center based on magnetic flux concentration effect

At a Glance

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

Technical Documentation: Enhanced NV Magnetometry via Magnetic Flux Concentration

6CCVD Material Analysis & Sales Documentation

This document analyzes the research “Enhancement of magnetic detection by ensemble NV color center based on magnetic flux concentration effect” (Acta Physica Sinica, 2021) and outlines how 6CCVD’s advanced MPCVD diamond materials and customization capabilities can support the replication and extension of this high-sensitivity quantum sensing technology.

Executive Summary

This research successfully demonstrates a method for significantly enhancing the magnetic sensitivity of ensemble Nitrogen-Vacancy (NV) diamond sensors using a Magnetic Flux Concentrator (MFC) structure.

Core Achievement: Validation of the magnetic flux concentration effect using paired T-shaped MFCs integrated with ensemble NV diamond for wide-field magnetic imaging.
Methodology: Continuous Wave Optical Detection Magnetic Resonance (CW-ODMR) imaging was used to measure the magnetic field enhancement factor (N).
Performance Gain (Measured): Magnetic sensitivity was improved by a factor of 3.67, increasing from a baseline of 1.10 nT/Hz^1/2 to a measured 0.30 nT/Hz^1/2 (at 1.0 mm MFC gap).
Enhancement Factor: A measured magnetic enhancement factor (N) of 10.35 was achieved at a 1.0 mm MFC gap.
Predicted Optimization: Modeling predicts that optimizing the MFC gap to 0.5 mm would yield an enhancement factor of 18.21 and a corresponding sensitivity of 0.25 nT/Hz^1/2.
Material Requirement: The success relies critically on high-quality, high-concentration ensemble NV diamond, a specialty material provided by 6CCVD.

Technical Specifications

The following hard data points were extracted from the research paper detailing the experimental setup and performance metrics:

Parameter	Value	Unit	Context
Baseline Magnetic Sensitivity (No MFC)	1.10	nT/Hz^1/2	System without Magnetic Flux Concentrator
Measured Magnetic Sensitivity (1.0 mm Gap)	0.30	nT/Hz^1/2	Achieved with MFC structure
Estimated Magnetic Sensitivity (0.5 mm Gap)	0.25	nT/Hz^1/2	Predicted optimal performance
Measured Enhancement Factor (1.0 mm Gap)	10.35	Dimensionless	Ratio of enhanced field to reference field
Estimated Enhancement Factor (0.5 mm Gap)	18.21	Dimensionless	Predicted optimal enhancement
NV Diamond Sample Dimensions	1.0 x 4.0 x 0.5	mm	Long strip shape
NV Color Center Concentration	~3	ppm	High concentration ensemble diamond
Diamond Growth Face	(100)	Crystallographic Plane	Used for NV axis alignment
ODMR Microwave Frequency Range	2.7 - 3.0	GHz	CW-ODMR sweep range
Excitation Laser Wavelength	532	nm	Green laser
Fluorescence Detection Wavelength	~670	nm	Red fluorescence (Approximation)

Key Methodologies

The experiment utilized a wide-field magnetic imaging system combined with custom MFC structures to validate the enhancement effect.

Material Selection: A high-concentration ensemble NV diamond sample (approx. 3 ppm NV concentration) grown on a (100) face was used. The sample dimensions were 1.0 mm x 4.0 mm x 0.5 mm.
MFC Fabrication: Paired T-shaped MFC structures were designed via COMSOL simulation and fabricated from 1J79 Permalloy, a high magnetic permeability soft magnetic material (μ_r = 10000 used in simulation).
Optical System: A 532 nm green laser was used for NV center excitation. Red fluorescence (~670 nm) was collected via a 20x/0.4 objective lens and split between a camera (for imaging) and a photodetector (for normalization).
Microwave Delivery: A microwave source (ROHDE & SCHWARZ SMA 100A, 30 dBm output) delivered frequencies between 2.7 GHz and 3.0 GHz via a microwave antenna positioned near the diamond.
Magnetic Field Generation: A pair of cylindrical permanent magnets (Ø40 x 10 mm) configured in a pseudo-Helmholtz arrangement provided the static magnetic field (B₀ ≈ 5 Gs at the center).
Data Acquisition: CW-ODMR wide-field imaging was performed, with the camera exposure time set to 5 ms. Data was averaged over 5 measurements to improve accuracy.
Analysis: ODMR curves were fitted using a dual-peak Lorentz formula. The magnetic field (B_n) was calculated from the resonance frequency difference (Δx) between the two peaks. The enhancement factor (N) was determined by comparing B_m (with MFC) to B_f (without MFC).

6CCVD Solutions & Capabilities

This research highlights the critical role of high-quality diamond material in achieving state-of-the-art quantum sensing performance. 6CCVD is uniquely positioned to supply and customize the necessary MPCVD diamond substrates to replicate and advance this work.

Applicable Materials

To replicate or extend this research, high-quality, high-concentration ensemble NV centers are required. 6CCVD recommends the following materials:

Optical Grade SCD (Single Crystal Diamond): Ideal for maximizing coherence time (T₂) and minimizing background noise, crucial for achieving the highest possible magnetic sensitivity (η).
High-Concentration Ensemble PCD (Polycrystalline Diamond): Suitable for large-area, wide-field imaging applications (up to 125 mm wafers) where high NV density is prioritized for signal contrast (C).
Custom NV Doping: 6CCVD offers precise control over nitrogen incorporation during MPCVD growth, allowing researchers to target specific NV concentrations (e.g., the 3 ppm used in this study) to optimize the trade-off between sensitivity and spatial resolution.

Customization Potential

The integration of the diamond sensor with the MFC structure requires precise material dimensions and surface preparation. 6CCVD’s custom capabilities directly address these needs:

Research Requirement	6CCVD Customization Service	Benefit to Researcher
Specific Dimensions (1.0 x 4.0 x 0.5 mm)	Custom Dimensions & Thickness: We supply SCD and PCD plates/wafers with thicknesses ranging from 0.1 µm up to 500 µm (0.5 mm) and substrates up to 10 mm.	Ensures perfect geometric fit and alignment with external MFC structures and optical systems.
High Photon Collection Efficiency (R)	Advanced Polishing: Ultra-low surface roughness (Ra < 1 nm for SCD; Ra < 5 nm for inch-size PCD).	Maximizes the photon collection rate (R) and contrast (C), directly improving the calculated magnetic sensitivity (η).
Future Integrated Microwave Structures	Custom Metalization: Internal capability for depositing Au, Pt, Pd, Ti, W, and Cu films.	Allows for the integration of on-chip microwave delivery structures (e.g., CPW lines) directly onto the diamond surface, eliminating the need for external antennas and improving microwave efficiency.

Engineering Support

The successful creation of high-performance NV sensors involves complex material science, including controlled nitrogen doping, irradiation, and annealing processes.

6CCVD’s in-house PhD team specializes in MPCVD growth parameters and NV physics. We offer consultation services to assist engineers and scientists in selecting the optimal diamond material (SCD vs. PCD, doping level, crystal orientation) required for similar weak magnetic field detection and quantum sensing projects.
We ensure global delivery (DDU default, DDP available) of high-specification diamond materials, supporting international research efforts without logistical delays.

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

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/Hz1/2 to 0.30 nT/Hz1/2. 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 MFC’s 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/Hz1/2. 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.

Tech Support

Original Source

DOI: https://doi.org/10.7498/aps.70.20210129