Resonant paramagnetic enhancement of the thermal and zero-point Nyquist noise

The interaction between a very thin macroscopic solenoid, and a single magn etic particle precessing in a external magnetic held B-0, is described by t aking into account the thermal and the zero-point fluctuations of stochasti c electrodynamics. The inductor belongs to a RLC circuit without batteries and the random motion of the magnetic dipole generates in the solenoid a fl uctuating current I-dip(t), and a fluctuating voltage epsilon(dip)(t), With spectral distribution quite different from the Nyquist noise. We show that the mean square value [I-dip(2)] presents an enormous variation when the f requency of precession approaches the frequency of the circuit, but it is s till much smaller than the Nyquist current in the circuit, However, we also show that [I-dip(2)] can reach measurable values if the inductor is intera cting with a macroscopic sample of magnetic particles (atoms or nuclei) whi ch are close enough to its coils. (C) 1999 Published by Elsevier Science B. V.