  Antiferromagnetic spin rings represent prototypical realizations of highly
correlated, low-dimensional systems. Here we theoretically show how the
introduction of magnetic defects by controlled chemical substitutions results
in a strong spatial modulation of spin-pair entanglement within each ring.
Entanglement between local degrees of freedom (individual spins) and collective
ones (total ring spins) are shown to coexist in exchange-coupled ring dimers,
as can be deduced from general symmetry arguments. We verify the persistence of
these features at finite temperatures, and discuss them in terms of
experimentally accessible observables.
