6 research outputs found
Spin Glasses: Model systems for non-equilibrium dynamics
Spin glasses are frustrated magnetic systems due to a random distribution of
ferro- and antiferromagnetic interactions. An experimental three dimensional
(3d) spin glass exhibits a second order phase transition to a low temperature
spin glass phase regardless of the spin dimensionality. In addition, the low
temperature phase of Ising and Heisenberg spin glasses exhibits similar
non-equilibrium dynamics and an infinitely slow approach towards a
thermodynamic equilibrium state. There are however significant differences in
the detailed character of the dynamics as to memory and rejuvenation phenomena
and the influence of critical dynamics on the behaviour. In this article, some
aspects of the non-equilibrium dynamics of an Ising and a Heisenberg spin glass
are briefly reviewed and some comparisons are made to other glassy systems that
exhibit magnetic non-equilibrium dynamics.Comment: To appear in J. Phys.: Condens. Matter, Proceedings from HFM2003,
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Strong rejuvenation in a chiral-glass superconductor
The glassy paramagnetic Meissner phase of a BiSrCaCuO
superconductor ( = 8.18) is investigated by squid magnetometry, using
``dc-memory'' experiments employed earlier to study spin glasses. The
temperature dependence of the zero-field-cooled and thermo-remanent
magnetization is recorded on re-heating after specific cooling protocols, in
which single or multiple halts are performed at constant temperatures. The
'spin' states equilibrated during the halts are retrieved on re-heating. The
observed memory and rejuvenation effects are similar to those observed in
Heisenberg-like spin glasses.Comment: REVTeX 4 style; 5 pages, 5 figure
Atomic force microscopy adhesion mapping: revealing assembly process in inorganic systems
There are still many unknowns regarding assembly processes. In this work, we demonstrate the capability of atomic force microscopy (AFM) adhesion mapping in revealing the conditions that promote the light-induced assembly of nanoparticles (NPs) on nanostructured surfaces in inorganic systems, both in macroand nanodomains. Gold (Au) NPs and zinc oxide (ZnO) nanostructures are employed as the model materials, and different characterization techniques are used for extracting the relationship between the materials' crystallinity, stoichiometry, and morphology as well as surface adhesion mapping information. The light-induced assembly of Au NPs is associated with the attraction forces between the opposite surface charges of the NPs and preferential ZnO sites, which can be identified by adhesion mapping. We show that the yield of Au nanoclusters assembled onto the ZnO surface depends on the crystallinity and stoichiometry of ZnO and is not due to the roughness of the surface. The presented experiments demonstrate that AFM adhesion mapping can be used as an invaluable tool for predicting the strength and directions of assembly processes