NMR spectroscopy with force-gradient detection on a GaAs epitaxial layer

Area of Science:

• Physics
• Materials Science
• Spectroscopy

Background:

• Nuclear Magnetic Resonance (NMR) spectroscopy typically requires highly homogeneous background magnetic fields (B0).
• Achieving high-resolution NMR on microscale samples presents significant challenges due to field inhomogeneity and detection sensitivity.
• Existing methods struggle to reconcile the need for B0 homogeneity with localized magnetic field gradients.

Purpose of the Study:

• To demonstrate a novel force-gradient magnetic resonance detection scheme for nanoscale NMR.
• To achieve high-resolution (69)Ga NMR on a 35 μm(3) GaAs sample.
• To overcome the limitations of magnetic field homogeneity in nanoscale NMR.

Main Methods:

• Utilized a single crystal silicon cantilever tipped with a nickel sphere for force-gradient detection.
• Employed a sample shuttling technique to separate polarization and detection phases, managing magnetic field gradients.
• Implemented a sequence of radiofrequency pulses and adiabatic rapid passage (ARP) sweeps for spin manipulation and Free Induction Decay (FID) measurement.

Main Results:

• Successfully performed (69)Ga NMR spectroscopy on a 35 μm(3) GaAs epitaxial layer at 5K and 5T.
• Achieved a spectral linewidth on the order of 10 kHz, demonstrating high resolution.
• Registered spin state changes as measurable shifts in the cantilever's resonant frequency.

Conclusions:

• The developed force-gradient magnetic resonance detection scheme is effective for nanoscale NMR.
• Sample shuttling is a viable strategy to mitigate magnetic field gradient issues in high-resolution nanoscale NMR.
• This technique opens new avenues for probing nuclear spins in materials at the microscale.