Relaxometry and Dephasing Imaging of Superparamagnetic Magnetite Nanoparticles Using a Single Qubit

Area of Science:

• Quantum sensing
• Nanotechnology
• Magnetism

Background:

• Superparamagnetic nanoparticles exhibit complex magnetic dynamics.
• Nitrogen-vacancy (NV) centers in diamond are sensitive quantum probes.
• Characterizing nanoscale magnetic properties is crucial for various applications.

Purpose of the Study:

• To investigate the magnetic dynamics of a single superparamagnetic nanoparticle using NV center relaxometry.
• To develop a method for determining nanoparticle size and distance from the NV center.
• To explore the anisotropy of NV sensitivity in magnetic measurements.

Main Methods:

• Utilized scanning probe relaxometry with a single nitrogen vacancy (NV) center in diamond.
• Measured spin noise by characterizing the relaxation (T1) and dephasing (T2) times of the NV center.
• Applied an Ornstein-Uhlenbeck model to analyze nanoparticle fluctuations and extract parameters.

Main Results:

• Successfully characterized the spin noise of a single 10 nm magnetite nanoparticle.
• Demonstrated the anisotropy of NV sensitivity based on the decoherence measurement method.
• Accurately extracted nanoparticle diameter and distance from the NV center.

Conclusions:

• Scanning probe relaxometry with NV centers is a powerful tool for characterizing magnetic nanoparticles.
• This technique offers potential for future applications in medical diagnostics and fundamental magnetic research.
• The method provides a non-invasive way to probe nanoscale magnetic behavior.