  The efficiency of the adiabatic demagnetization of nuclear spin system (NSS)
of a solid is limited, if quadrupole effects are present. Nevertheless, despite
a considerable quadrupole interaction, recent experiments validated the
thermodynamic description of the NSS in GaAs. This suggests that nuclear spin
temperature can be used as the universal indicator of the NSS state in presence
of external perturbations. We implement this idea by analyzing the modification
of the NSS temperature in response to an oscillating magnetic field at various
frequencies, an approach termed as the warm-up spectroscopy. It is tested in a
n-GaAs sample where both mechanical strain and built-in electric field may
contribute to the quadrupole splitting, yielding the parameters of electric
field gradient tensors for 75As and both Ga isotopes, 69Ga and 71Ga.
