  We analytically express the loss of entanglement between the components of a
quantum device due to the generation of quantum correlations with its
environment, and show that such loss diminishes when the latter is macroscopic
and displays a semi-classical behaviour. We model the problem as a device made
of a couple of qubits with a magnetic environment: this choice allows us to
implement the above condition of semi-classical macroscopicity in terms of a
large-S condition, according to the well known equivalence between classical
and $S \rightarrow \infty$ limit. A possible strategy for protecting internal
entanglement exploiting the mechanism of domain-formation typical of critical
dynamics is also suggested.
