Quantification of Entanglement from Magnetic Susceptibility for a   Heisenberg Spin 1/2 system
  Temperature and magnetic field dependent magnetization and extraction of entanglement from the experimental data is reported for dichloro(thiazole)copper(II), a Heisenberg spin chain system. The magnetic susceptibility vs. temperature plot exhibits signature of infinite spin chain. Isothermal magnetization measurements (as a function of magnetic field) were performed at various temperatures below the antiferromagnetic (AFM) ordering, where the AFM correlations persist significantly. These magnetization curves are fitted to the theoretically generated Bonner-Fisher model. Magnetic susceptibility can be used as a macroscopic witness of entanglement; using which entanglement is extracted from the experimentally measured magnetic data. 
Tanmoy Chakraborty, Harkirat Singh, Diptaranjan Das, Tamal K. Sen,   Swadhin K. Mandal, Chiranjib Mitra
cond-mat.str-el