  Magnetic Resonance Force Microscopy can enable nanoscale imaging of spin
lifetime. We report temperature dependent measurements of the spin correlation
time $\tau_m$ of the statistical fluctuations of the spin polarization---the
spin noise---of ensembles containing $\sim 100$ electron spins by this
technique. Magneto-mechanical relaxation due to spin-cantilever coupling was
controlled and spurious mechanisms that can affect the spin correlation time of
the microscopic signal were characterized. These measurements have
ramifications for optimizing spin sensitivity, understanding local spin
dynamics and for nanoscale imaging.
