Long-range ferromagnetic dipolar ordering of high-spin molecular   clusters
  We report the first example of a transition to long-range magnetic order in a purely dipolarly interacting molecular magnet. For the magnetic cluster compound Mn6O4Br4(Et2dbm)6, the anisotropy experienced by the total spin S=12 of each cluster is so small that spin-lattice relaxation remains fast down to the lowest temperatures, thus enabling dipolar order to occur within experimental times at Tc = 0.16 K. In high magnetic fields, the relaxation rate becomes drastically reduced and the interplay between nuclear- and electron-spin lattice relaxation is revealed. 
A. Morello, F. L. Mettes, F. Luis, J. F. Fernandez, J. Krzystek, G.   Aromi, G. Christou, and L. J. de Jongh