Skip to content
6CCVD Research

Advancement in scanning magnetic microscopy utilizing high-sensitivity room-temperature TMR sensors for geological applications

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2024-12-22
JournalEarth Planets and Space
AuthorsHirokuni Oda, Seiji Kumagai, Kosuke Fujiwara, Hitoshi Matsuzaki, Hiroshi Wagatsuma
InstitutionsIbaraki University, Tohoku University
Citations2
AnalysisFull AI Review Included

Technical Documentation & Analysis: High-Sensitivity Magnetic Microscopy

Section titled “Technical Documentation & Analysis: High-Sensitivity Magnetic Microscopy”

Executive Summary

Section titled “Executive Summary”

This documentation analyzes the advancements in scanning magnetic microscopy (SMM) using room-temperature Tunnel Magneto-Resistance (TMR) sensors, highlighting the material requirements and positioning 6CCVD’s advanced MPCVD diamond solutions for next-generation sensor development.

  • Core Achievement: Demonstrated high-sensitivity, room-temperature TMR sensors as a viable alternative to cryogenic SQUID systems for geological SMM.
  • Sensitivity Metrics: Achieved magnetic field sensitivities better than 30 nT/√Hz at 1 Hz (10-point average) using the 1073 ”m sensor.
  • Noise Reduction: RMS noise levels were significantly reduced to 5.87 nT (0.1-2.5 Hz band, 10-point average) for the longer sensor, comparable to or better than previously reported TMR systems.
  • Application Focus: The technology is critical for submillimeter-scale magnetostratigraphy and paleomagnetic studies, requiring a target field sensitivity of < 5 nT and spatial resolution of 50-200 ”m.
  • Material Opportunity: The paper identifies Quantum Diamond Devices (QDDs) as a highly sensitive, room-temperature competitor. 6CCVD’s Electronic Grade Single Crystal Diamond (SCD) is the foundational material for QDD development.
  • 6CCVD Value: We offer the high-purity SCD substrates, precision polishing (Ra < 1 nm), and custom metalization required to optimize sensor performance and achieve the target sub-nT resolution.

Technical Specifications

Section titled “Technical Specifications”

The following table summarizes the key performance metrics and physical parameters achieved or targeted in the research:

ParameterValueUnitContext
Sensor Length (Sensor #1)1073”mUsed for high sensitivity evaluation.
Sensor Length (Sensor #2)357”mUsed for high spatial resolution evaluation.
Raw Sensitivity (Sensor #1)< 200nT/√HzMeasured at 1 Hz, 50 Hz sampling.
Averaged Sensitivity (Sensor #1)< 30nT/√Hz10 points average, measured at 1 Hz.
RMS Noise (Sensor #1, Averaged)5.87nTFrequency band 0.1-2.5 Hz, 10 points average.
Target Field Sensitivity< 5nTDesirable goal for submillimeter magnetostratigraphy.
Target Spatial Resolution50-200”mDesirable goal for imaging ultrafine-scale magnetic stripes.
Minimum Lift-off Distance ($h$)100”mSimilar to minimum lift-offs for SQUID microscope (SSM).
Scanning Grid Resolution0.1mmUsed for magnetic field mapping of basalt thin section.
Estimated Magnetic Moment Sensitivity ($m_{min}$)4.0 × 10-13Am2Calculated at 100 ”m lift-off, sufficient for most paleomagnetic studies.
DC-Amplifier Gain Range40, 60, 80, 100dBUsed for signal amplification.

Key Methodologies

Section titled “Key Methodologies”

The experimental setup focused on adapting existing high-precision scanning hardware (SSM XYZ stage) for room-temperature TMR sensor evaluation, emphasizing noise reduction and data correlation.

  1. Sensor Architecture: TMR sensors (1073 ”m and 357 ”m long) composed of serially connected TMR elements were utilized. The flux concentrator was intentionally removed to optimize for high spatial resolution required for microscopy.
  2. Scanning Platform: An XYZ stage and controller, originally developed for a Scanning SQUID Microscope (SSM), were employed. The sensors were housed in a two-layered magnetic shield.
  3. Measurement Configuration: The vertically upward magnetic field component ($B_{z}$) was scanned approximately 0.3 mm above the sample (Hawaiian basalt thin section).
  4. Electronics Integration: TMR sensors were connected to the analog voltage input via a DC-preamplifier (based on a Wheatstone bridge circuit) and a DC-amplifier.
  5. Calibration: Sensors were calibrated using a precision current source (3 mA line current) and fitted to a theoretical curve for an infinite line current.
  6. Data Acquisition: Scanning was conducted on 0.1 mm grids. The nominal sampling frequency was 50 Hz, with noise reduction achieved by performing 10-point averaging over continuous measurements.
  7. Data Correlation: TMR magnetic images were compared against established SQUID-acquired magnetic field maps after applying Upward Continuation (to adjust for lift-off differences) and Convolution (to simulate the integration effect along the TMR sensor length).

6CCVD Solutions & Capabilities

Section titled “6CCVD Solutions & Capabilities”

This research validates the market demand for high-resolution, room-temperature magnetic sensors for geological and biomedical applications. While the paper focuses on TMR, it explicitly mentions Quantum Diamond Devices (QDDs) as a sensitive, quantum-based alternative. 6CCVD provides the critical MPCVD diamond materials necessary to advance QDD technology beyond current TMR limitations.

Applicable Materials

Section titled “Applicable Materials”

To replicate or extend this research, particularly toward the ultimate goal of sub-nT resolution and 50-200 ”m spatial resolution, 6CCVD recommends the following materials for QDD development:

  • Electronic Grade Single Crystal Diamond (SCD): Essential for QDDs utilizing Nitrogen-Vacancy (NV) centers. Our high-purity SCD minimizes background defects, maximizing NV center coherence time, which is critical for achieving ultra-high magnetic field sensitivity (sub-nT range).
  • Optical Grade SCD: Required if the QDD system utilizes optical readout (laser light sources, as noted in the paper). Our optical grade material ensures low absorption and high transmission efficiency for the necessary excitation and detection wavelengths.

Customization Potential

Section titled “Customization Potential”

The success of high-resolution SMM relies on precise sensor geometry and integration. 6CCVD’s advanced manufacturing capabilities directly address the customization needs of TMR, SQUID, and QDD systems:

Research Requirement6CCVD CapabilityTechnical Advantage
Sensor DimensionsCustom Plates/Wafers up to 125mm (PCD) and large SCD plates.We supply SCD/PCD substrates tailored to specific sensor array sizes, accommodating the need for both long (1073 ”m) and short (357 ”m) sensor elements.
Surface QualityPolishing to Ra < 1 nm (SCD) and Ra < 5 nm (Inch-size PCD).Ultra-low surface roughness is critical for minimizing the sensor-to-sample lift-off distance ($h$), directly improving magnetic moment sensitivity ($m_{min}$) by a factor of $h^{3}$.
Sensor IntegrationIn-house Metalization Services (Au, Pt, Pd, Ti, W, Cu).We apply custom metal contacts and interconnects directly onto the diamond surface, facilitating the integration of TMR electrodes or microwave/readout structures required for QDDs.
Thickness ControlSCD/PCD thickness control from 0.1 ”m to 500 ”m.Precise thickness is vital for managing thermal properties and ensuring optimal NV center depth control within QDD architectures.

Engineering Support

Section titled “Engineering Support”

The authors conclude that “Further improvements can be made by optimizing the sensors, preamplifiers, measurement systems, and post-processing software.”

6CCVD’s in-house PhD material science team specializes in optimizing diamond properties for quantum and electronic applications. We provide consultative support for projects targeting:

  • Ultra-High Sensitivity: Assisting researchers in selecting the optimal SCD grade and processing parameters necessary to maximize NV center density and coherence for sub-nT magnetic field detection.
  • High Spatial Resolution: Providing custom laser cutting and dicing services to achieve the required 50-200 ”m spatial resolution targets for advanced magnetostratigraphy projects.
  • Cryogen-Free Solutions: Supporting the shift away from labor-intensive cryogenic SQUID systems by supplying the core material for robust, room-temperature QDD sensors.

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

View Original Abstract

Abstract Scanning magnetic microscopes enable high-sensitivity mapping of magnetic fields in thin geological sections, facilitating submillimeter- to submicrometer-scale studies of paleomagnetism and rock magnetism. Magnetic fields of geological samples have been mapped using various sensors, including Hall-effect devices, magneto-impedance devices, superconducting quantum interference devices (SQUIDs), quantum diamond devices, and tunnel magneto-resistance (TMR) devices. This study proposes magnetic microscopy using high-sensitivity room-temperature TMR sensors developed for biomagnetic applications. The goal was to create high-performance magnetic microscopes that do not require labor-intensive techniques, such as cryogenic technology. An XYZ stage developed for a scanning SQUID microscope (SSM) was used to demonstrate and evaluate magnetic microscopy with TMR sensors. The original TMR sensors developed for biomagnetic sensing composed of serially connected TMR elements with a total length of 2684 ÎŒm were shortened to 1073 ÎŒm (Sensor #1) and 357 ÎŒm length (Sensor #2). Background measurements at 50 Hz show magnetic field sensitivities better than 200 nT/√Hz and 600 nT/√Hz at 1 Hz for Sensor #1 and Sensor #2, respectively. By averaging 10 points of the original 50 Hz sampling, magnetic field sensitivities are better than 30 nT/√Hz and 90 nT/√Hz at 1 Hz for Sensor #1 and Sensor #2, respectively. To demonstrate TMR sensors as magnetic microscopes, a vertically magnetized Hawaii basalt thin section was measured and compared with a SQUID-acquired magnetic field map. Magnetic scanning images obtained with TMR sensors on a 0.1-mm grid were compared with those of SSM after adjusting the lift-off by upward continuation and integrated along the length of the sensors. The results demonstrated that magnetic images for 1073-ÎŒm-long (357 ÎŒm-long) TMR sensors aligned along the y-axis and x-axis are consistent with those after upward continuation to 0.3 mm (0.25 mm) and 0.4 mm (0.25 mm) and convolution by 1 × 10 (1 × 4) and 10 × 1 (4 × 1) matrix, respectively. Overall, the high-sensitivity TMR sensors exhibited promising performance. Further improvements can be made by optimizing the sensors, preamplifiers, and measurement systems for magnetic microscopy to achieve an optimum target resolution. Graphical Abstract

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 1996 - Potential theory in gravity and magnetic applications

Reads Similar to This

Scattering of Ultrashort X-ray Pulses from Oriented NV Centers in the Diamond Structure DC Magnetometry at the $T_2$ Limit 5 nm-scale surface evenness movement measurement method based on the electron spin in diamond