Resonant Spin Tunneling in Randomly Oriented Nanospheres of Mn$_{12}$   Acetate
  We report measurements and theoretical analysis of resonant spin tunneling in randomly oriented nanospheres of a molecular magnet. Amorphous nanospheres of Mn$_{12}$ acetate have been fabricated and characterized by chemical, infrared, TEM, X-ray, and magnetic methods. Magnetic measurements have revealed sharp tunneling peaks in the field derivative of the magnetization that occur at the typical resonant field values for Mn$_{12}$ acetate. Theoretical analysis is provided that explains these observations. We argue that resonant spin tunneling in a molecular magnet can be established in a powder sample, without the need for a single crystal and without aligning the easy magnetization axes of the molecules. This is confirmed by re-analyzing the old data on a powdered sample of non-oriented micron-size crystals of Mn$_{12}$ acetate. Our findings can greatly simplify the selection of candidates for quantum spin tunneling among newly synthesized molecular magnets. 
S. Lendinez, R. Zarzuela, J. Tejada, M. W. Terban, S. J. L. Billinge,   J. Espin, I. Imaz, D. Maspoch, E. M. Chudnovsky
cond-mat.mes-hall