Magnetic domains and domain wall pinning in atomically thin CrBr3 revealed by nanoscale imaging
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-03-31 |
| Journal | Nature Communications |
| Authors | Qiâchao Sun, Tiancheng Song, Eric Anderson, Andreas Brunner, Johannes Förster |
| Institutions | University of Stuttgart, National Institute for Materials Science |
| Citations | 107 |
| Analysis | Full AI Review Included |
6CCVD Technical Analysis: Nanoscale Magnetic Imaging via NV Diamond Probes
Section titled â6CCVD Technical Analysis: Nanoscale Magnetic Imaging via NV Diamond ProbesâThis document analyzes the research paper âMagnetic domains and domain wall pinning in atomically thin CrBr3 revealed by nanoscale imagingâ (Nature Communications, 2021) to highlight the critical role of high-quality Single Crystal Diamond (SCD) in advanced quantum sensing applications and to demonstrate 6CCVDâs capability to supply the necessary materials and custom fabrication services.
Executive Summary
Section titled âExecutive SummaryâThe study successfully employs cryogenic scanning magnetometry utilizing a single Nitrogen-Vacancy (NV) center in a diamond probe to achieve unprecedented nanoscale resolution in two-dimensional (2D) magnetic materials.
- High Sensitivity Quantum Sensing: Achieved optimal magnetic field sensitivity of ~0.3 ”THz-1, essential for probing weak stray fields from atomically thin van der Waals (vdW) magnets.
- Nanoscale Resolution: Demonstrated high spatial resolution (~80 nm), enabling the direct imaging of magnetic domains and the precise localization of defect sites responsible for domain wall pinning in CrBr3 bilayers.
- Pulsed ODMR Scheme: Utilized a pulsed optically detected magnetic resonance (ODMR) scheme to significantly reduce microwave heating, maintaining the sample temperature near the base cryostat temperature (<5 K).
- Quantitative Magnetization Mapping: Provided quantitative measurement of the saturation magnetization of the CrBr3 bilayer, determined to be approximately 26 ”Bnm-2.
- Material Requirement: The technique relies fundamentally on high-purity, single-crystal diamond (SCD) probes with precisely engineered NV centers and custom geometries (etched pillars/cantilevers).
- Core Finding: Confirmed that domain wall pinning, driven by material defects, is the dominant coercivity mechanism in atomically thin CrBr3.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the methodology and results sections, demonstrating the performance achieved using the NV diamond probe setup.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Magnetic Field Sensitivity (Optimal) | 0.3 | ”THz-1 | Achieved using pulsed ODMR scheme |
| Spatial Resolution (NV-Sample Distance) | ~80 | nm | Determined by the distance between the NV center and the CrBr3 sample |
| Measurement Temperature (Base) | < 5 | K | Liquid helium bath cryostat operation |
| CrBr3 Bilayer Saturation Magnetization | ~26 | ”Bnm-2 | Determined from reconstructed magnetization statistics |
| NV Center Axis Angle | ~54.7 | ° | Relative to the vertical direction in (100)-oriented diamond |
| Microwave $\pi$-Pulse Duration | ~80 | ns | Used for spin manipulation in pulsed ODMR |
| Laser Pulse Duration (Readout) | 600 | ns | Used for optical initialization and readout |
| Sample Heating (Pulsed vs. CW) | Few hundred | milli-Kelvin | Temperature increase above 4.2 K base temperature |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized a highly specialized cryogenic scanning NV magnetometry setup, requiring precise material engineering and advanced pulse control.
- Diamond Probe Integration: A single NV center (14N) was implanted in the apex of a pillar etched from a diamond cantilever, which was attached to a tuning fork for Atomic Force Microscopy (AFM) operation in frequency modulation mode.
- Cryogenic Environment: The system was housed in a liquid helium bath cryostat (T < 5 K) with vector superconducting coils to apply external magnetic fields (Bext).
- Sample Preparation: Atomically thin CrBr3 was encapsulated between hexagonal boron nitride (hBN) flakes and transferred onto a coplanar waveguide (V/Au, 10/200 nm) in an inert gas glovebox (<0.1 p.p.m. H2O/O2) to prevent degradation.
- Pulsed ODMR Sequence: Stray magnetic fields were mapped using a pulsed ODMR scheme, applying short laser pulses and microwave $\pi$-pulses (600 ns and 80 ns, respectively) to avoid power broadening and minimize laser/microwave-induced heating.
- Magnetic Field Alignment: The external magnetic field was set parallel to the NV axis (~54.7°) to simplify the spin state analysis and avoid mixing of spin states.
- Data Processing: Stray magnetic field maps were reconstructed into quantitative magnetization images using a reverse-propagation protocol, assuming out-of-plane magnetization.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research demonstrates the critical need for ultra-high-quality, custom-engineered diamond materials for cutting-edge quantum sensing and nanoscale magnetometry. 6CCVD is uniquely positioned to supply the foundational materials and specialized fabrication required to replicate or advance this work.
Applicable Materials
Section titled âApplicable MaterialsâTo achieve the high sensitivity and low noise floor necessary for NV magnetometry, the highest quality diamond is mandatory.
- Optical Grade Single Crystal Diamond (SCD): Required for NV center creation. 6CCVD supplies high-purity SCD substrates necessary for low-strain, high-coherence NV centers, ensuring the optimal 0.3 ”THz-1 sensitivity achieved in this study can be matched or exceeded.
- Custom Substrates: We offer SCD substrates up to 500 ”m thick, or thicker substrates (up to 10 mm) for robust cantilever/probe fabrication, ensuring mechanical stability in cryogenic environments.
Customization Potential
Section titled âCustomization PotentialâThe complexity of the NV probe geometry (etched pillars, cantilever integration) and the microwave delivery system (coplanar waveguide) directly align with 6CCVDâs advanced fabrication capabilities.
| Research Requirement | 6CCVD Customization Capability | Benefit to the Researcher |
|---|---|---|
| Custom Probe Geometry | Precision laser cutting and etching services. | Enables the creation of custom cantilever shapes and etched pillars for NV placement, optimizing tip-sample distance (e.g., achieving the required ~80 nm working distance). |
| Surface Quality | Polishing to Ra < 1 nm (SCD). | Ensures minimal surface defects and low optical scattering, critical for efficient optical detection of the NV spin state in the confocal microscope setup. |
| Metalization for CPW | Internal metalization services (Au, Pt, Pd, Ti, W, Cu). | We can deposit custom metal stacks (e.g., V/Au used in the paper) directly onto diamond or auxiliary substrates for integrated microwave coplanar waveguides (CPW) or ohmic contacts. |
| Large Area PCD | Plates/wafers up to 125 mm (PCD). | While SCD is used for the sensor, large-area PCD can be supplied for robust, thermally conductive heat sinks or specialized packaging in complex cryogenic setups. |
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD material science team provides authoritative support for complex quantum projects.
- Material Selection for Quantum Sensing: Our experts can assist researchers in selecting the optimal SCD grade (e.g., low nitrogen content, specific crystallographic orientation) to maximize NV coherence time and magnetic field sensitivity for similar Cryogenic Scanning Magnetometry projects.
- Integration Consultation: We offer consultation on post-processing techniques, including surface termination and metalization strategies, crucial for integrating diamond probes into existing AFM/cryostat systems.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.