AVS 49th International Symposium
    Molecular and Bio-Magnetism Tuesday Sessions
       Session MB+BI+OF-TuA

Invited Paper MB+BI+OF-TuA1
Single-Molecule Magnets: A Molecular Approach to Nanoscale Magnetic Materials

Tuesday, November 5, 2002, 2:00 pm, Room C-205

Session: Molecular and Bio-Magnetism
Presenter: G. Christou, University of Florida
Authors: G. Christou, University of Florida
M. Soler, University of Florida
N. Aliaga-Alcalde, University of Florida
S. Bhaduri, University of Florida
W. Wernsdorfer, Laboratoire Louis Neel - CNRS, France
D.N. Hendrickson, University of California at San Diego
Correspondent: Click to Email
Single-molecule magnets (SMMs) are molecules that function as single-domain magnetic particles which, below their blocking temperature, exhibit the classical macroscale property of a magnet, namely magnetization hysteresis.@footnote 1@ SMMs owe their properties to a combination of a large ground state spin value and easy-axis-type anisotropy, which give a significant barrier to magnetization relaxation. SMMs thus represent a molecular (or bottom up) approach to new nanoscale magnetic materials, offering all the advantages of molecular chemistry (room temperature synthesis, purity, solubility in many solvents, a well defined periphery of organic groups, a crystalline ensemble of monodisperse units) as well as displaying the superparamagnetism of a mesoscale magnetic particle. They also display quantum tunneling of magnetization (QTM), emphasizing that they straddle the interface between the classical and quantum regimes. SMMs have many potential applications, but these require that their properties be both understood and controlled, particularly QTM. The Mn12 SMMs are the best understood. Various derivatives have been prepared differing in the organic groups, and it has been discovered that the magnetic properties (including QTM) can be significantly altered. This is also possible by adding additional electrons, and both the [Mn12]- (S = 19/2) and [Mn12]2- (S = 10) versions have been prepared. Mn4 SMMs with S = 9/2 have also been extensively studied. In some cases, two Mn4 SMMs occur as supramolecular dimers, [Mn4]2, and exchange interactions between them lead to interesting modifications of their QTM properties, establishing the feasibility of tuning the QTM in SMMs.@footnote 2@ @FootnoteText@ @footnote 1@ G. Christou, D. Gatteschi, D. N. Hendrickson, and R. Sessoli, MRS Bulletin 25, 66 (2000).@footnote 2@ W. Wernsdorfer, N. Aliaga-Alcalde, D. N. Hendrickson, and G. Christou, Nature 416, 406 (2002).