LAUSR

Exact analytical diagonalization is used to study the bipartite entanglement of the antiferromagnetic mixed spin(1/2,S ) Heisenberg dimer (MSHD) with the help of negativity. Under the assumption of uniaxial single-ion anisotropy affecting higher spin-S (S > 1/2) entities only, the ground-state degeneracy 2S is partially lifted and the ground state is two-fold degenerate with the total magnetization per dimer ±(S −1/2). It is shown that the largest quantum entanglement is reached for the antiferromagnetic ground state of MSHD with arbitrary half-odd-integer spins S , regardless of the exchange and single-ion anisotropies. Contrary to this, the degree of a quantum entanglement in MSHD with an integer spin S for the easy-plane single-ion anisotropy, exhibits an increasing tendency with an obvious spin-S driven crossing point. It is shown that the increasing spin magnitude is a crucial driving mechanism for an enhancement of a threshold temperature above which the thermal entanglement vanishes. The easy-plane single-ion anisotropy together with an enlargement of the spin-S magnitude is other significant driving mechanism for an enhancement of the thermal entanglement in MSHD.