Dipolar Ordering and Quantum Dynamics of Domain Walls in Mn-12 Acetate
  We find that dipolar interactions favor ferromagnetic ordering of elongated crystals of Mn12 Acetate below 0.8 K. Ordered crystals must possess domain walls. Motion of the wall corresponds to a moving front of Landau-Zener transitions between quantum spin levels. Structure and mobility of the wall are computed. The effect is robust with respect to inhomogeneous broadening and decoherence. 
D. A. Garanin and E. M. Chudnovsky