Entanglement, purity and fidelity in the anisotropy (1/2,1) mixed-spin system

We study entanglement, purity and fidelity in the anisotropy (1/2,1) mixed-spin Heisenberg chain. We find that negativity, as a measure of entanglement, displays a dip at the SU(2) isotropic point of the system, which is in contrast to the peak appearance of concurrence in the spin-1/2 XXZ chain. Moreover, at the isotropic point, purity gives a minimum, while the mixed-state fidelity susceptibility emerges a maximum.