Coherent effects in polarized systems of nuclear or electron spins using a microscopic model are studied, but not the Bloch equations. It is shown that the spin system in a resonance circuit can emit a coherent superradiant pulse when the system is initially in an essentially unstable state, at a time much shorter than the spin dephasing time T2 when the coupling of the system with the circuit is sufficiently strong, and at the time longer than T2 when this coupling is weak. The important role if dipole spin-spin interactions is elucidated.
T. S. Belozerova,
V. K. Henner,
V. I. Yukalov,
"Computer simulation of spin superradiance", Proc. SPIE 2098, Computer Simulation in Nonlinear Optics, (3 May 1994); doi: 10.1117/12.175149; https://doi.org/10.1117/12.175149