Magnetic resonance force microscopy in fast-relaxing spins using a frequency-modulation mode detection method

We describe a magnetic resonance force microscopy experiment carried out using both a fast-relaxing spin system and a frequency-modulation mode detection method, presenting a validation of the measured signal and sensitivity. The detection method applied along with a self-excited cantilever oscillation worked stably without any serious interference due to spurious cantilever excitation despite application of first-harmonic microwave modulation, and thereby successfully created almost the maximum available signal. The signal could be measured without distortion while the magnetic field was swept at a rate of 1.9 G s-1. The measured sensitivity approached the thermal noise limit of the cantilever with a high quality factor. The experimental results for both signal and noise were in good agreement with theoretical predictions