Adiabatic demagnetization and generation of entanglement in spin systems

We study the entanglement emergence in a dipolar-coupled nuclear spin-1/2 system cooled using the adiabatic demagnetization technique. The unexpected behavior of entanglement for the next- and next–next-neighbor spins is revealed: entangled states of a spin system appear in two distinct temperature and magnetic field regions separated by a zero-concurrence area. The magnetic field dependence of the concurrence can have two maximums which positions are determined by the initial conditions and number of spins in a chain. -- Highlights: ► We study entanglement in a spin system cooled using an adiabatic demagnetization. ► Entangled states appear in two separated regions of temperature and magnetic field. ► The adiabatic demagnetization is a way to the experimental testing of entanglement.