Landau-Zener tunneling with many-body quantum effects in crystals of   molecular magnets
  We present a quantum interpretation of the heights in hysteresis of $Fe_{8}$ molecule at lower temperatures by treating the crystal as an Ising spin system with the dipolar interaction between spins. Then we apply it to two limit cases : rapid and adiabatic regions. Our theoretical analysis is in agreement with the experimental observation in these regions, which indicates that the steps in hysteresis loops of magnetization of Fe$_{8}$ at lower temperatures show a pure quantum process. 
Li-Bin Fu, Shi-Gang Chen, and Bambi Hu