Super-Resolution Diamond Magnetic Microscopy of Superparamagnetic Nanoparticles

Area of Science:

• Physics
• Materials Science
• Nanotechnology

Background:

• Scanning-probe and wide-field magnetic microscopy using nitrogen-vacancy (NV) centers in diamond offer advanced capabilities but have limitations.
• Existing methods face challenges in resolution, sensitivity, or complexity for nanoscale magnetic imaging.

Purpose of the Study:

• To develop an alternative nanoscale magnetic microscopy technique with improved resolution and sensitivity.
• To image magnetic fields from individual nanoparticles using optical control of NV centers.

Main Methods:

• Implemented a novel method combining donut-beam super-resolution with optically detected magnetic resonance spectroscopy.
• Utilized optically controlled nitrogen-vacancy (NV) centers in a dense layer near the diamond surface.
• Imaged magnetic fields from single 30 nm iron-oxide nanoparticles.

Main Results:

• Achieved a lateral spatial resolution of approximately 100 nm.
• Resolved individual magnetic dipole features from nanoparticle clusters with spacings down to 190 nm.
• Demonstrated magnetic feature amplitudes an order of magnitude larger than confocal microscopy due to improved optical point-spread function and shallow NV depth.

Conclusions:

• The developed magnetic microscope offers a promising new format for nanoscale magnetic imaging.
• The signal-to-noise ratio for nanoparticle detection remains robust even with improved spatial resolution.
• Identified background fluorescence sources (diamond Raman emission, imperfect NV charge control) as limitations for further performance enhancement.