  The ongoing exploration of the ambiguous boundary between the quantum and the
classical worlds has spurred substantial developments in quantum science and
technology. Recently, the nonclassicality of dynamical processes has been
proposed from a quantum-information-theoretic perspective, in terms of
witnessing nonclassical correlations with Hamiltonian ensemble simulations. To
acquire insights into the quantum-dynamical mechanism of the process
nonclassicality, here we propose to investigate the nonclassicality of the
electron spin free-induction-decay process associated with an NV$^-$ center. By
controlling the nuclear spin precession dynamics via an external magnetic field
and nuclear spin polarization, it is possible to manipulate the dynamical
behavior of the electron spin, showing a transition between classicality and
nonclassicality. We propose an explanation of the classicality-nonclassicality
transition in terms of the nuclear spin precession axis orientation and
dynamics. We have also performed a series of numerical simulations supporting
our findings. Consequently, we can attribute the nonclassical trait of the
electron spin dynamics to the behavior of nuclear spin precession dynamics.
