  Motivated by the discovery of fully open-flavor tetraquark states $X_0(2900)$
and $X_1(2900)$ by the LHCb Collaboration, the magnetic dipole moment of the
$X_1(2900)$ state with the quantum numbers $ J^{P} = 1^{-}$ is determined in
the diquark-antidiquark picture using the light-cone sum rules. The numerical
result is obtained as $ \mu_{X_1}=0.79^{+0.36}_{-0.39}\,\mu_N$. The magnetic
moments of hadrons encompasses useful knowledge on the distributions of charge
and magnetization their inside, which can be used to better understand their
geometrical shapes and quark-gluon organizations. The observation of the
$X_0(2900)$ and $X_1(2900)$ as the first two fully open-flavor multiquark
states has opened a new window for investigation of the exotic states. The
obtained results in the present study may shed light on the future experimental
and theoretical searches on the properties of fully open-flavor multiquark
states.
