All-Optical Vector Magnetometry Based on Level Anticrossing Spectroscopy of Spin Centers in 4H-SiC

At a Glance

Metadata	Details
Publication Date	2025-09-01
Journal	Journal of Experimental and Theoretical Physics Letters
Authors	K. V. Likhachev, M. V. Uchaev, M.M. Loginova, Igor P. Veyshtort, A. P. Bundakova
Analysis	Full AI Review Included

Executive Summary

This research presents a novel all-optical vector magnetometer utilizing S = 3/2 vacancy centers (V2 centers) in 4H-SiC, offering significant advantages over traditional diamond-based systems.

Microwave-Free Operation: The system relies entirely on Level Anticrossing (LAC) spectroscopy detected via photoluminescence (PL), eliminating the need for microwave power. This simplifies the instrument design and prevents sample heating.
High Sensitivity: Achieves a sensitivity of 0.1 µT/√(Hz) for the longitudinal magnetic field component (B_z) and 0.01 mT/√(Hz) for angular parameters (polar and azimuth angles).
Accelerated Vector Measurement: The introduction of calibrated “modifying” magnetic fields (B^mod) significantly accelerates the determination of the external field vector components (B_x, B_y, B_z), reducing the number of required iterative measurements.
High Spatial Resolution: The method provides micron and submicron spatial resolution, confirming its promise for microelectronics and biomedical diagnostics.
Robust Platform: SiC vacancy centers are inherently suitable for operation in high-temperature and high-radiation environments, expanding the application scope beyond typical quantum sensors.

Technical Specifications

Parameter	Value	Unit	Context
Sensor Material	4H-SiC	N/A	V2 vacancy centers (S = 3/2)
Operating Temperature	300	K	Room temperature operation
B_z Sensitivity	0.1	µT/√(Hz)	Longitudinal component sensitivity
Angular Sensitivity (θ, φ)	0.01	mT/√(Hz)	Polar and azimuth angles
Spatial Resolution (Confocal)	~1	µm	Resolution of the scanning confocal microscope
Spatial Resolution (Potential)	Submicron	N/A	Demonstrated capability for future applications
Excitation Laser Wavelength	785	nm	PL excitation source
Excitation Laser Power	150	mW	Used for PL excitation
Defect Creation Fluence	~10¹⁸	cm^-2	2-MeV electron irradiation dose
Fine Structure Splitting (2D)	23.4 x 10^-4	cm^-1	Equivalent to 70 MHz
Hyperfine Interaction (A)	~9	MHz	Interaction with single ²⁹Si nucleus
Modulation Field Amplitude	10	mT	Used for synchronous detection
Modulation Field Frequency	~1	kHz	Used for synchronous detection

Key Methodologies

The vector magnetometry relies on the unique spin properties of V2 centers in 4H-SiC and the precise measurement of Level Anticrossing (LAC) spectra.

Sensor Fabrication: 4H-SiC crystals, grown via the sublimation “sandwich method,” were irradiated with 2-MeV electrons to a fluence of ~10¹⁸ cm^-2 to create the S = 3/2 V2 vacancy centers.
Optical Setup: A confocal microscope setup (resolution ~1 µm) was used, employing a 785 nm, 150 mW laser for continuous PL excitation and an avalanche photodiode (APD) for infrared detection.
Signal Acquisition: LAC spectra were recorded by scanning a quasi-stationary magnetic field (B₀) along the c-axis (z-axis). The signal was modulated (10 mT amplitude, ~1 kHz frequency) and detected using a synchronous detector to obtain the first derivative of the PL intensity change.
Longitudinal Component (B_z) Measurement: B_z is determined by measuring the displacement of the main LAC points (LAC1 and LAC2) relative to a known reference spectrum.
Transverse Component (B_⊥) Magnitude Measurement: The magnitude of the transverse field (B_⊥) is determined by analyzing the change in intensity and shape of the satellite lines in the LAC spectrum (which arise from hyperfine interactions).
Vector Component Determination (B_x, B_y): To determine the azimuth angle (φ) and the B_x and B_y components, calibrated “modifying” magnetic fields (B^mod_x and B^mod_y) are sequentially applied. This allows B_x and B_y to be calculated directly from the resulting field magnitudes (B₁ and B₂) using established formulas, significantly reducing measurement time compared to iterative compensation methods.
Verification: The calculated external field components (B_x, B_y, B_z) are verified by applying a compensating magnetic field via Helmholtz coils; successful compensation results in the final LAC spectrum matching the zero-field reference spectrum.

Commercial Applications

The all-optical vector magnetometry technique based on 4H-SiC V2 centers is highly relevant for several high-tech industries, particularly those requiring robust, high-resolution sensing.

Quantum Sensing and Metrology:
- Development of compact, stable magnetic field and temperature sensors.
- Implementation of optical spectroscopy of hyperfine interactions for fundamental physics research.
Microelectronics and Semiconductor Diagnostics:
- Non-invasive visualization of magnetic domains and electric currents in integrated circuits (IC) with submicron spatial resolution.
- Diagnostics of semiconductor devices operating under high-temperature or high-radiation stress.
Biomedical and Life Sciences:
- Highly sensitive measurement of low magnetic fields for non-invasive diagnostics.
- Detection of magnetic resonance signals from individual electron or nuclear spins in complex biological molecules.
Aerospace and Defense:
- Magnetic field sensors capable of operating reliably in extreme conditions, such as high-radiation environments (outer space).
Quantum Computing:
- Readout of classical or quantum bits of information encoded in electron or nuclear spin memory.

View Original Abstract

An all-optical vector magnetometer based on paramagnetic color centers with the spin S = 3/2 in 4H-SiC silicon carbide is presented. The corresponding magnetometry method is based on level anticrossing spectroscopy and does not require the application of microwave power, unlike magnetometry based on optically detected magnetic resonance of nitrogen-vacancy centers in diamond. This eliminates sample heating and simplifies the design of the instrument. It has been shown that the use of “modifying” magnetic fields makes it possible to accelerate the measurement of external magnetic fields with high accuracy. Optical detection of level anticrossing signals in the infrared range provides micron and submicron spatial resolution, which makes the method promising for applications in microelectronics and biomedicine.

Tech Support

Original Source

DOI: https://doi.org/10.1134/s0021364025608164