Density Functional Theory of Molecular Magnets
Abstract
Observation of resonant tunneling of magnetization in molecular nanomagnets has focused significant attention on a novel class of spin-ordered organometallic molecules. These molecular magnets consist of approximately 70-200 atoms and are typically composed of 4-15 transition metal atoms locked in place by organic ligands and anions. In addition to very interesting physics and chemistry, such molecular systems could form the basis of future nanoscale devices. The fundamental figure of merit that determines the resonant tunneling fields and magnetic reorientation temperature is the second-order magnetic anisotropy Hamiltonian which is primarily determined by the spin orbit interaction. However many other factors contribute to the tunnel splittings. Such interactions include spin vibron interactions, higher-order electronic interactions, solvent- and defect-induced symmetry breaking, and coupling between spin-ordering and anisotropic effects. I will discuss a new method for the density-functional-based determination of second-order magnetic anisotropies and discuss some recent calculations on the interactions of import to tunnel splittings. In addition the density functional determination of Heisenberg Hamiltonians and possible ways for simultaneous inclusion of anisotropy and exchange will be discussed. Calculations presented will primarily concentrate on applications to Mn12-Acetate, the Co4 molecular magnet and the Mn4 dimer. References: M.R. Pederson and S.N. Khanna, PRB 60, 9566 (1999); M.R. Pederson, N. Bernstein and J. Kortus, PRL 89, 097202 (2002); J. Kortus, M.R. Pederson, T. Baruah, N. Bernstein and C.S. Hellberg, Polyhedron 22, 1871 (2003); K. Park, M.R. Pederson, S.L. Richardson, N. Aliaga-Alcade and G. Christou, PRB 68, 020405 (2003).
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MAR.A6003P