  Finite temperature effects in electromagnetic transitions in nuclei
contribute to many aspects of nuclear structure and astrophysically relevant
nuclear reactions. While electric dipole transitions have already been
extensively studied, the temperature sensitivity of magnetic transitions
remains largely unknown. This work comprises the study of isovector magnetic
dipole excitations (M1) occurring between spin-orbit (SO) partner states using
the recently developed self-consistent finite temperature relativistic
quasiparticle random phase approximation (FT-RQRPA) in the temperature range
from $T=$ 0 to 2 MeV. The M1 strength distributions of $^{40-60}$Ca and
$^{100-140}$Sn isotopic chains exhibit a strong temperature dependence. The M1
strength peaks shift significantly towards the lower energies due to the
decrease in SO splitting energies and weakening of the residual interaction,
especially above the critical temperatures ($T_\textrm{c}$) where the pairing
correlations vanish. By exploring the relevant two-quasiparticle ($2qp$)
configurations contributing to the M1 strength of closed- and open-shell
nuclei, new proton and neutron excitation channels between SO partners are
observed in low- and high-energy regions due to the thermal unblocking effects
around the Fermi level. At higher temperatures, we have noticed an interesting
result in $^{40,60}$Ca nuclei, the appearance of M1 excitations, which are
forbidden at zero temperature due to fully occupied (or fully vacant)
spin-orbit partner states.
