Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magic angle effects in a trigonal Mn(III)3 cluster: deconstruction of a
  single-molecule magnet   We present angle-dependent high-frequency EPR studies on a single-crystal of
a trigonal Mn3 cluster with an unusual structure in which the local magnetic
easy-axes of the constituent Mn(III) ions are tilted significantly away from
the molecular C3 axis towards the magic-angle of 54.7 degrees, resulting in an
almost complete cancelation of the 2nd-order axial magnetic anisotropy
associated with the ferromagnetically coupled total spin ST = 6 ground state.
This contrasts the situation in many related Mn3 single-molecule magnets (SMMs)
that have been studied intensively in the past, for which the local MnIII
anisotropy tensors are reasonably parallel, resulting in substantial barriers
to magnetization relaxation (Ueff = 30 to 35 cm 1) and magnetization blocking
below about 2.5 K. The suppression of the 2nd-order anisotropy in the present
case results in a situation in which the zero-field splitting (ZFS) of the ST =
6 ground state is dominated by 4th- and higher-order interactions. This
provides a unique opportunity to study in depth how molecular geometry
influences these interactions that are responsible for quantum tunneling of
magnetization in high-symmetry SMMs. Angle-dependent EPR measurements provide a
full mapping of the molecular magneto-anisotropy. Meanwhile, irreducible tensor
operator (ITO) methods are employed in order to obtain analytic expressions
that directly relate molecular anisotropy to the microscopic physics, i.e., the
ZFS tensors associated with the individual MnIII ions, their orientations, and
the exchange coupling between the three spins. We find that the magic-angle
tilting leads to a massive compression of the ST = 6 ground state energy level
diagram and strong mixing between spin projection states. Although these
characteristics are antagonistic to SMM behavior, they provide important
insights into the physics of polynuclear molecular nanomagnets.

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The categories of this paper are: dg-ga
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: mtrl-th
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The categories of this paper are: comp-gas
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The categories of this paper are: nlin
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: hep-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th
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The categories of this paper are: econ
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The categories of this paper are: q-bio
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The categories of this paper are: chem-ph