452 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
Origin and spectroscopic determination of trigonal anisotropy in a heteronuclear single-molecule magnet
W-band ({\nu} ca. 94 GHz) electron paramagnetic resonance (EPR) spectroscopy
was used for a single-crystal study of a star-shaped Fe3Cr single-molecule
magnet (SMM) with crystallographically imposed trigonal symmetry. The high
resolution and sensitivity accessible with W-band EPR allowed us to determine
accurately the axial zero-field splitting terms for the ground (S =6) and first
two excited states (S =5 and S =4). Furthermore, spectra recorded by applying
the magnetic field perpendicular to the trigonal axis showed a pi/6 angular
modulation. This behavior is a signature of the presence of trigonal transverse
magnetic anisotropy terms whose values had not been spectroscopically
determined in any SMM prior to this work. Such in-plane anisotropy could only
be justified by dropping the so-called 'giant spin approach' and by considering
a complete multispin approach. From a detailed analysis of experimental data
with the two models, it emerged that the observed trigonal anisotropy directly
reflects the structural features of the cluster, i.e., the relative orientation
of single-ion anisotropy tensors and the angular modulation of single-ion
anisotropy components in the hard plane of the cluster. Finally, since
high-order transverse anisotropy is pivotal in determining the spin dynamics in
the quantum tunneling regime, we have compared the angular dependence of the
tunnel splitting predicted by the two models upon application of a transverse
field (Berry-phase interference).Comment: 13 pages, 9 figure
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
Storage and retrieval of microwave pulses with molecular spin ensembles
Abstract
Hybrid architectures combining complementary quantum systems will be largely used in quantum technologies and the integration of different components is one of the key issues. Thanks to their long coherence times and the easy manipulation with microwave pulses, electron spins hold a potential for the realization of quantum memories. Here, we test diluted oxovanadium tetraphenyl porphyrin (VO(TPP)) as a prototypical molecular spin system for the Storage/Retrieval of microwave pulses when embedded into planar superconducting microwave resonators. We first investigate the efficiency of several pulse sequences in addressing the spins. The Carr-Purcell and the Uhrig Dynamical Decoupling enhance the memory time up to three times with three π pulses. We then successfully store and retrieve trains of up to 5 small pulses by using a single recovery pulse. These results demonstrate the memory capabilities of molecular spin ensembles when embedded into quantum circuits
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