  Magnetic dipole (M1) excitations build not only a fundamental mode of
nucleonic transitions, but they are also relevant for nuclear astrophysics
applications. We have established a theory framework for description of M1
transitions based on the relativistic nuclear energy density functional. For
this purpose the relativistic quasiparticle random phase approximation (RQRPA)
is established using density dependent point coupling interaction DD-PC1,
supplemented with the isovector-pseudovector interaction channel in order to
study unnatural parity transitions. The introduced framework has been validated
using the M1 sum rule for core-plus-two-nucleon systems, and employed in
studies of the spin, orbital, isoscalar and isovector M1 transition strengths,
that relate to the electromagnetic probe, in magic nuclei $^{48}$Ca and
$^{208}$Pb, and open shell nuclei $^{42}$Ca and $^{50}$Ti. In these systems,
the isovector spin-flip M1 transition is dominant, mainly between one or two
spin-orbit partner states. It is shown that pairing correlations have a
significant impact on the centroid energy and major peak position of the M1
mode. The M1 excitations could provide an additional constraint to improve
nuclear energy density functionals in the future studies.

Nuclear Theory;Nuclear Experiment