Thermal Entanglement in Spin-Dimer V⁴⁺ with a Strong Magnetic Field

We study the entanglement in Heisenberg dimer single molecular magnets V⁴⁺ with a strong magnetic field by means of the measure of entanglement called “concurrence”and find that thermal entanglement exists for both the ferromagnetic (FM) and antiferromagnetic (AFM) cases. In the FM case, entanglement vanishes for anisotropic parameter λ = 0 while in the AFM case, entanglement exits in the whole region of anisotropic parameter 0 ≤ λ ≤ 1. Entanglement variations with anisotropic parameter λ, magnetic field B and temperature T are evaluated. We find a critical magnetic field at which the concurrence changes sharply from zero to maximum entanglement.