@article{ISI:000271982000032,
 abstract = {We present here a theoretical approach to compute the molecular magnetic
anisotropy parameters, D (M) and E (M) for single molecule magnets in
any given spin eigenstate of exchange spin Hamiltonian. We first
describe a hybrid constant M (S) -valence bond (VB) technique of solving
spin Hamiltonians employing full spatial and spin symmetry adaptation
and we illustrate this technique by solving the exchange Hamiltonian of
the Cu6Fe8 system. Treating the anisotropy Hamiltonian as perturbation,
we compute the D (M) and E (M) values for various eigenstates of the
exchange Hamiltonian. Since, the dipolar contribution to the magnetic
anisotropy is negligibly small, we calculate the molecular anisotropy
from the single-ion anisotropies of the metal centers. We have studied
the variation of D (M) and E (M) by rotating the single-ion anisotropies
in the case of Mn12Ac and Fe-8 SMMs in ground and few low-lying excited
states of the exchange Hamiltonian. In both the systems, we find that
the molecular anisotropy changes drastically when the single-ion
anisotropies are rotated. While in Mn12Ac SMM D (M) values depend
strongly on the spin of the eigenstate, it is almost independent of the
spin of the eigenstate in Fe-8 SMM. We also find that the D (M) value is
almost insensitive to the orientation of the anisotropy of the core
Mn(IV) ions. The dependence of D (M) on the energy gap between the
ground and the excited states in both the systems has also been studied
by using different sets of exchange constants.},
 author = {Ramasesha, S. and Sahoo, Shaon and Raghunathan, Rajamani and Sen,
Diptiman},
 doi = {10.1007/s12039-009-0098-4},
 eissn = {0973-7103},
 issn = {0974-3626},
 journal = {JOURNAL OF CHEMICAL SCIENCES},
 month = {SEP},
 number = {5},
 orcid-numbers = {Sahoo, Shaon/0000-0003-0299-3408},
 pages = {823-837},
 times-cited = {0},
 title = {Computing magnetic anisotropy constants of single molecule magnets},
 unique-id = {ISI:000271982000032},
 volume = {121},
 year = {2009}
}