The manganese oxo-cluster, [Mn 12 O 12 (O 2 CMe) 16 (H 2 O) 4 ]‚2(HO 2 CMe)‚4(H 2 O), (Mn-12), has been the subject of intense interest for its novel magnetic properties.Although it is a model system for nanoscale magnetic data storage, no methods for forming films or attaching the cluster to surfaces have been reported. Here we demonstrate a simple approach using functionalized self-assembled monolayers and short-chain polyelectrolytes to make monolayer and nanometer-scale multilayer films of Mn-12.The discovery of unusual magnetic behavior in the manganese oxo-cluster, [Mn 12 O 12 (O 2 CMe) 16 (H 2 O) 4 ]‚2(HO 2 CMe)‚ 4(H 2 O) (Mn-12), was significant in that it allowed for the first observation of quantum tunneling of magnetization. 1 The evidence for tunneling is discrete steps in magnetization as a function of the field in the hysteresis loop. The magnetic properties also provide support for the fact that a single molecule has the potential to act like a nanoscale magnet. For example, the orientation of the magnetic moment of an individual Mn-12 molecule has an extremely slow relaxation time (on the order of months at 2 K) after the magnetic field has been removed. 2 Although the Mn 12 O 12 core mimics a tiny bar magnet, investigations have shown that the nature of the ligand, cocrystallized solvent, and cluster isomerization can effect the rate of resonant magnetization tunneling. 3,4 Studies in which the acetate group has been exchanged for a variety of encapsulating carboxylic acids have concluded that the ligand can both control the solubility of the cluster and tune the redox potential of the metal centers. As a model system for nanostructured data storage, one of the goals yet to be realized is a method for patterning Mn-12 clusters on a surface in a controlled fashion. Recent work has been directed toward the discovery of new clusters with enhanced properties. 5 Before practical devices can be fabricated, however, it will be important to identify means for structuring these clusters into nanoscale architectures. Although elegant synthetic work has shown that it is possible to functionalize Mn-12 selectively (with the potential for attaching a tether to the cluster), 6 binding the complex to surfaces has not yet been demonstrated. Clearly, synthetic methodologies to form nanostructured, functional magnetic and electronic materials are an important goal not only for data storage but for a variety of practical applications. 7 Previous approaches to patterning a surface with nanoparticles have relied on hydrophilic and hydrophobic interactions. For example, a self-assembled monolayer (SAM) film formed by alkanethiolates with different terminal chemical functionalities was used to wet the substrate surface selectively, controlling the areal deposition of iron oxides from colloidal solutions.

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Our ac susceptibility (χ) measurements, carried out between 1.7 and 100 K, show five χ peaks, signaling five transition temperatures, in the disordered frustrated spinel ferrite Co2TiO4. This result, in conjunction with the replica symmetric mean field theory of vector spin glasses and earlier magnetization and neutron diffraction studies, indicates a separate freezing of A- and B-site spins. To our knowledge, such a phenomenon has not been observed before. Co2SnO4 and Co1.2Zn0.8TiO4 χ measurements, where three and one χ peaks are respectively observed, support this picture.