Progress on Magnetic Resonance Force Microscopy Detection of Statistical Polarization of Electron Spins

Here we report our experimental progress on detecting statistical polarization of electron spins. In the condition of low external magnetic field and high temperature, polarizati on due to Boltzman factor could be small, i.e. $\mu B/k_BT \ll 1 $. The $\sqrt{N}$ statistical polarization can dominate the Boltzmann polariation when the spins ensemble is suffi ciently small. With its unprecedented force sensitivity, Magnetic Resonance Force Microscopy (MRFM) has demonstrated the capability to observe this self-polarizing nature of spins via the i-OSCAR detection protocol\footnote {H.J. Mamin, R. Budakian, B.W. Chui and D. Rugar, Phys. Rev. Lett. \textbf{91}, 207604 (2003)}. Our efforts to use MRFM to detect this statistical polarization will be presented.