63 research outputs found
Frequency Dependence of Aging, Rejuvenation and Memory in a disordered ferroelectric
We characterize in details the aging properties of the ferroelectric phase of
K Ta_{1-x} Nb_x O_3 (KTN), where both rejuvenation and (partial) memory are
observed. In particular, we carefully examine the frequency dependence of
several quantities that characterize aging, rejuvenation and memory. We find a
marked subaging behaviour, with an a.c. dielectric susceptiblity scaling as
, where is the waiting time. We suggest an
interpretation in terms of pinned domain walls, much along the lines proposed
for aging in a disordered ferromagnet, where both domain wall reconformations
and overall (cumulative) domain growth are needed to rationalize the
experimental findings.Comment: submitted to EPJ
When Mass Spectrometry Meets Nanoparticles. Weighing, Manipulating and Fragmenting Single Nanoparticles in The Gas Phase
A new mass spectrometer based on charge detection has been developed. It enables the determination of mass distribution of various macromolecules and nanoparticles. By using an ion trap coupled to a CO2 laser, photoinduced dissociation of such macroions can be studied at the single ion level giving uniquely access to intrinsic features such as fragmentation patterns and unimolecular dissociation activation energy
When Mass Spectrometry Meets Nanoparticles. Weighing, Manipulating and Fragmenting Single Nanoparticles in The Gas Phase
A new mass spectrometer based on charge detection has been developed. It enables the determination of mass distribution of various macromolecules and nanoparticles. By using an ion trap coupled to a CO2 laser, photoinduced dissociation of such macroions can be studied at the single ion level giving uniquely access to intrinsic features such as fragmentation patterns and unimolecular dissociation activation energy
Symmetrical Temperature-Chaos Effect with Positive and Negative Temperature Shifts in a Spin Glass
The aging in a Heisenberg-like spin glass Ag(11 at% Mn) is investigated by
measurements of the zero field cooled magnetic relaxation at a constant
temperature after small temperature shifts . A
crossover from fully accumulative to non-accumulative aging is observed, and by
converting time scales to length scales using the logarithmic growth law of the
droplet model, we find a quantitative evidence that positive and negative
temperature shifts cause an equivalent restart of aging (rejuvenation) in terms
of dynamical length scales. This result supports the existence of a unique
overlap length between a pair of equilibrium states in the spin glass system.Comment: 4 page
Numerical Study of Aging in the Generalized Random Energy Model
Magnetizations are introduced to the Generalized Random Energy Model (GREM)
and numerical simulations on ac susceptibility is made for direct comparison
with experiments in glassy materials. Prominent dynamical natures of spin
glasses, {\it i.e.}, {\em memory} effect and {\em reinitialization}, are
reproduced well in the GREM. The existence of many layers causing continuous
transitions is very important for the two natures. Results of experiments in
other glassy materials such as polymers, supercooled glycerol and orientational
glasses, which are contrast to those in spin glasses, are interpreted well by
the Single-layer Random Energy Model.Comment: 8 pages, 9 figures, to be submitted to J. Phys. Soc. Jp
Mean-field theory of temperature cycling experiments in spin-glasses
We study analytically the effect of temperature cyclings in mean-field
spin-glasses. In accordance with real experiments, we obtain a strong
reinitialization of the dynamics on decreasing the temperature combined with
memory effects when the original high temperature is restored. The same
calculation applied to mean-field models of structural glasses shows no such
reinitialization, again in accordance with experiments. In this context, we
derive some relations between experimentally accessible quantities and propose
new experimental protocols. Finally, we briefly discuss the effect of field
cyclings during isothermal aging.Comment: Some misprints corrected, references updated, final version to apper
in PR
Optical extinction and scattering cross sections of plasmonic nanoparticle dimers in aqueous suspension
Absolute extinction and scattering cross sections for gold nanoparticle dimers were determined experimentally using a chemometric approach involving singular-value decomposition of the extinction and scattering spectra of slowly aggregating gold nanospheres in aqueous suspension. Quantitative spectroscopic data on plasmonic nanoparticle assemblies in liquid suspension are rare, in particular for particles larger than 40 nm, and in this work we demonstrate how such data can be obtained directly from the aggregating suspension. Our method can analyse, non invasively, the evolution of several sub-populations of nanoparticle assemblies. It may be applied to other self-assembling nanoparticle systems with an evolving optical response. The colloidal systems studied here are based on 20, 50 and 80 nm gold nanospheres in aqueous solutions containing sodium lipoate. In these systems, the reversible dimerisation process can be controlled using pH and ionic strength, and this control is rationalised in terms of DLVO theory. The dimers were identified in suspension by their translational and rotational diffusion through scattering correlation spectroscopy. Moreover, their gigadalton molecular weight was measured using electrospray charge-detection mass spectrometry, demonstrating that mass spectrometry can be used to study nanoparticles assemblies of very high molecular mass. The extinction and scattering cross sections calculated in the discrete-dipole approximation (DDA) agree very well with those obtained experimentally using our approach
Aging in KLiTa0: a domain growth interpretation
The aging behaviour of the a.c. susceptibility of randomly substituted
KLiTa0 crystals reveals marked differences with spin-glasses in
that cooling rate effects are very important. The response to temperature steps
(including temperature cycles) was carefully studied. A model based on
thermally activated domain growth accounts for all the experimental results,
provided one allows for a large distribution of pinning energies, in such a way
that `slow' and `fast' domains coexist. Interesting similarities with deeply
supercooled liquids are underlined.Comment: 4 pages. Preprint LPTENS/9820, submitted to Phys. Rev. Let
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