3,312 research outputs found
Field dependent anisotropy change in a supramolecular Mn(II)-[3x3] grid
The magnetic anisotropy of a novel Mn(II)-[3x3] grid complex was investigated
by means of high-field torque magnetometry. Torque vs. field curves at low
temperatures demonstrate a ground state with S > 0 and exhibit a torque step
due to a field induced level-crossing at B* \approx 7.5 T, accompanied by an
abrupt change of magnetic anisotropy from easy-axis to hard-axis type. These
observations are discussed in terms of a spin Hamiltonian formalism.Comment: 4 pages, 4 figures, to be published in Phys. Rev. Let
Electron Spectroscopy and Density-Functional Study of "Ferric Wheel" Molecules
The Li-centered "ferric wheel" molecules with six oxo-bridged iron atoms form
molecular crystals. We probed their electronic structure by X-ray photoelectron
(XPS) and soft X-ray emission spectroscopy (XES), having calculated in parallel
the electronic structure of a single "ferric wheel" molecule from
first-principles by tools of the density-functional theory, using,
specifically, the Siesta method. The Fe local moments were found to be 4 mu_B,
irrespective of their mutual orientation. Neighbouring atoms, primarily oxygen,
exhibit a noticeable magnetic polarization, yielding effective spin S=5/2 per
iron atom, that can get inverted as a "rigid" one in magnetic transitions.
Corresponding energy preferences can be mapped onto the Heisenberg model with
effective exchange parameter J of about -80 K.Comment: 8 pages with 3 embedded postscript figures; uses elsart.cls;
contribution at the E-MRS 2003 Spring Meeting (Strasbourg, June 2003
Quantum tunneling of the Neel vector in antiferromagnetic [3 x 3] grid molecules
Based on numerical calculations it is shown that the antiferromagnetic grid
molecule Mn-[3 x 3] is a very promising candidate to experimentally detect the
phenomenon of quantum tunneling of the Neel vector.Comment: 4 pages, 3 figures, REVTEX 4, to appear in PR
Classification of Invariant Star Products up to Equivariant Morita Equivalence on Symplectic Manifolds
In this paper we investigate equivariant Morita theory for algebras with
momentum maps and compute the equivariant Picard groupoid in terms of the
Picard groupoid explicitly. We consider three types of Morita theory:
ring-theoretic equivalence, *-equivalence and strong equivalence. Then we apply
these general considerations to star product algebras over symplectic manifolds
with a Lie algebra symmetry. We obtain the full classification up to
equivariant Morita equivalence.Comment: 28 pages. Minor update, fixed typos
Improving ocean-glider's payload with a new generation of spectrophotometric PH sensor
Ocean gliders have clearly become nowadays useful autonomous
platforms addressed to measure a wide range of seawater parameters in a more
sustainable and efficient way. This new ocean monitoring approach has implied
the need to develop smaller, faster and more efficient sensors without reducing key
features like accuracy, resolution, time-response, among others, in order to fit the
glider operational capabilities. This work is aiming to present the latest development
stages of a new spectrophotometric pH sensor, its integration process into a Wave
Glider SV3 platform and the preliminary results derived from an offshore mission
performed in subtropical waters between the Canary Islands and Cape Verde
archipelagos.Peer Reviewe
Q-dependence of the inelastic neutron scattering cross section for molecular spin clusters with high molecular symmetry
For powder samples of polynuclear metal complexes the dependence of the
inelastic neutron scattering intensity on the momentum transfer Q is known to
be described by a combination of so called interference terms. They reflect the
interplay between the geometrical structure of the compound and the spatial
properties of the wave functions involved in the transition. In this work, it
is shown that the Q-dependence is strongly interrelated with the molecular
symmetry of molecular nanomagnets, and, if the molecular symmetry is high
enough, is actually completely determined by it. A general formalism connecting
spatial symmetry and interference terms is developed. The arguments are
detailed for cyclic spin clusters, as experimentally realized by e.g. the
octanuclear molecular wheel Cr8, and the star like tetranuclear cluster Fe4.Comment: 8 pages, 1 figures, REVTEX
- …