449 research outputs found
Patterning molecular scale paramagnets at Au Surface: A root to Magneto-Molecular-Electronics
Few examples of the exploitation of molecular magnetic properties in
molecular electronics are known to date. Here we propose the realization of
Self assembled monolayers (SAM) of a particular stable organic radical. This
radical is meant to be used as a standard molecule on which to prove the
validity of a single spin reading procedure known as ESR-STM. We also discuss a
range of possible applications, further than ESR-STM, of magnetic monolayers of
simple purely organic magnetic molecule.Comment: This preprint is currently partially under revisio
Quantum Double and Differential Calculi
We show that bicovariant bimodules as defined by Woronowicz are in one to one
correspondence with the Drinfeld quantum double representations. We then prove
that a differential calculus associated to a bicovariant bimodule of dimension
n is connected to the existence of a particular (n+1)--dimensional
representation of the double. An example of bicovariant differential calculus
on the non quasitriangular quantum group E_q(2) is developed. The construction
is studied in terms of Hochschild cohomology and a correspondence between
differential calculi and 1-cocycles is proved. Some differences of calculi on
quantum and finite groups with respect to Lie groups are stressed.Comment: Revised version with added cohomological analysis. 14 pages, plain
te
NMR and SR detection of unconventional spin dynamics in Er(trensal) and Dy(trensal) molecular magnets
Measurements of proton Nuclear Magnetic Resonance (1H NMR) spectra and
relaxation and of Muon Spin Relaxation (SR) have been performed as a
function of temperature and external magnetic field on two isostructural
lanthanide complexes, Er(trensal) and Dy(trensal) featuring
crystallographically imposed trigonal symmetry. Both the nuclear 1/T1 and muon
longitudinal relaxation rates, LRR, exhibit a peak for temperatures T
lower than 30K, associated to the slowing down of the spin dynamics, and the
width of the NMR absorption spectra starts to increase significantly at T ca.
50K, a temperature sizably higher than the one of the LRR peaks. The LRR peaks
have a field and temperature dependence different from those previously
reported for all Molecular Nanomagnets. They do not follow the
Bloembergen-Purcell-Pound scaling of the amplitude and position in temperature
and field and thus cannot be explained in terms of a single dominating
correlation time c determined by the spin slowing down at low
temperature. Further, for T lower than 50K the spectral width does not follow
the temperature behavior of the magnetic susceptibility chi. We suggest, using
simple qualitative considerations, that the observed behavior is due to a
combination of two different relaxation processes characterized by the
correlation times LT and HT, dominating for T lower than 30K and T
higher than 50K, respectively. Finally, the observed flattening of LRR for T
lower than 5K is suggested to have a quantum origin
Coherent coupling between Vanadyl Phthalocyanine spin ensemble and microwave photons: Towards integration of molecular spin qubits into quantum circuits
Electron spins are ideal two-level systems that may couple with microwave photons so that, under specific conditions, coherent spin-photon states can be realized. This represents a fundamental step for the transfer and the manipulation of quantum information. Along with spin impurities in solids, molecular spins in concentrated phases have recently shown coherent dynamics under microwave stimuli. Here we show that it is possible to obtain high cooperativity regime between a molecular Vanadyl Phthalocyanine (VOPc) spin ensemble and a high quality factor superconducting YBa2Cu3O7 (YBCO) coplanar resonator at 0.5 K. This demonstrates that molecular spin centers can be successfully integrated in hybrid quantum devices
Single-Ion Anisotropy and Intramolecular Interactions in CeIIIand NdIIIDimers
[Image: see text] This article reports the syntheses, characterization, structural description, together with magnetic and spectroscopic properties of two isostructural molecular magnets based on the chiral ligand N,N′-bis((1,2-diphenyl-(pyridine-2-yl)methylene)-(R,R/S,S)-ethane-1,2-diamine), L1, of general formula [Ln(2)(RR-L1)(2)(Cl(6))]·MeOH·1.5H(2)O, (Ln = Ce (1) or Nd (2)). Multifrequency electron paramagnetic resonance (EPR), cantilever torque magnetometry (CTM) measurements, and ab initio calculations allowed us to determine single-ion magnetic anisotropy and intramolecular magnetic interactions in both compounds, evidencing a more important role of the anisotropic exchange for the Nd(III) derivative. The comparison of experimental and theoretical data indicates that, in the case of largely rhombic lanthanide ions, ab initio calculations can fail in determining the orientation of the weakest components, while being reliable in determining their principal values. However, they remain of paramount importance to set the analysis of EPR and CTM on sound basis, thus obtaining a very precise picture of the magnetic interactions in these systems. Finally, the electronic structure of the two complexes, as obtained by this approach, is consistent with the absence of zero-field slow relaxation observed in ac susceptibility
Magnetic Anisotropy Trends along a Full 4f-Series: The fn+7Effect
[Image: see text] The combined experimental and computational study of the 13 magnetic complexes belonging to the Na[LnDOTA(H(2)O)] (H(4)DOTA = tetraazacyclododecane-N,N′,N″,N‴-tetraacetic acid and Ln = Ce–Yb) family allowed us to identify a new trend: the orientation of the magnetic anisotropy tensors of derivatives differing by seven f electrons practically coincide. We name this trend the f(n+7) effect. Experiments and theory fully agree on the match between the magnetic reference frames (e.g., the easy, intermediate, and hard direction). The shape of the magnetic anisotropy of some couples of ions differing by seven f electrons might seem instead different at first look, but our analysis explains a hidden similarity. We thus pave the way toward a reliable predictivity of the magnetic anisotropy of lanthanide complexes with a consequent reduced need of computational and synthetical efforts. We also offer a way to gain information on ions with a relatively small total angular momentum (i.e., Sm(3+) and Eu(3+)) and on the radioactive Pm(3+), which are difficult to investigate experimentally
Magnetic properties and spin dynamics in single molecule paramagnets Cu6Fe and Cu6Co
The magnetic properties and the spin dynamics of two molecular magnets have
been investigated by magnetization and d.c. susceptibility measurements,
Electron Paramagnetic Resonance (EPR) and proton Nuclear Magnetic Resonance
(NMR) over a wide range of temperature (1.6-300K) at applied magnetic fields,
H=0.5 and 1.5 Tesla. The two molecular magnets consist of
CuII(saldmen)(H2O)}6{FeIII(CN)6}](ClO4)38H2O in short Cu6Fe and the analog
compound with cobalt, Cu6Co. It is found that in Cu6Fe whose magnetic core is
constituted by six Cu2+ ions and one Fe3+ ion all with s=1/2, a weak
ferromagnetic interaction between Cu2+ moments through the central Fe3+ ion
with J = 0.14 K is present, while in Cu6Co the Co3+ ion is diamagnetic and the
weak interaction is antiferromagnetic with J = -1.12 K. The NMR spectra show
the presence of non equivalent groups of protons with a measurable contact
hyperfine interaction consistent with a small admixture of s-wave function with
the d-function of the magnetic ion. The NMR relaxation results are explained in
terms of a single ion (Cu2+, Fe3+, Co3+) uncorrelated spin dynamics with an
almost temperature independent correlation time due to the weak magnetic
exchange interaction. We conclude that the two molecular magnets studied here
behave as single molecule paramagnets with a very weak intramolecular
interaction, almost of the order of the dipolar intermolecular interaction.
Thus they represent a new class of molecular magnets which differ from the
single molecule magnets investigated up to now, where the intramolecular
interaction is much larger than the intermolecular one
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