NONLINEAR COUPLING AND RADIATION DAMPING IN OSCILLATOR-DETECTED MAGNETIC-RESONANCE OF SINGLE SPINS

We consider the effects of close coupling between magnetic spin system s and oscillator detectors. The scaling of present experiments using b oth mechanical and electrical oscillator detectors for single-spin det ection is examined. We show how nonlinear interactions ignored in prev ious descriptions may dominate the detector response in single-spin sc hemes using mechanical detectors. From a generalized form of the coupl ed Bloch equations, the difference between mechanical and electrical o scillator detection can be readily appreciated. Numerical solution of the coupled system using reasonable experimental parameters shows that complex dynamics may be observed in the single-spin detection scheme when the detector and the spin system are strongly coupled. The interp retation of spin system data obtained from the motion of a mechanical oscillator will require understanding of these detector effects. Chaot ic regimes are predicted in extreme cases. These results help both in identifying realistic limits of sensitivity for mechanical oscillator- detected magnetic resonance and in designing experimental methods to r ealize those limits.