Force detection of nuclear magnetic resonance using double-torsional micro-oscillators

The nuclear magnetic resonance of a sample of ammonium sulfate has been detected by coupling the magnetic force from the spins to a double torsional micro-oscillator. A single-sweep sensitivity of 3 × 10 −15 N/Hz1/2 was observed at room temperature for a sample-on-oscillator configuration. Microelectronic fabrication techniques were employed to create the high-Q single crystal silicon multiple torsional oscillators. With no sample mounted, the upper resonances of the oscillators were found to have force sensitivities as low as 1.5 × 10−16 N/Hz1/2 at room temperature. The design, fabrication, and characterization of these novel oscillators are discussed. Also, non-adiabaitc and relaxation effects on the observed force signal in nuclear magnetic resonance force miscroscopy are considered in detail.