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Topic: Geometrical frustration

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	Research Topics - Peter E. Schiffer
		The large degeneracy of states resulting from the geometrical frustration of competing interactions is an essential ingredient of important problems in fields as diverse as magnetism, protein folding, and neural networks.
		Geometrically frustrated magnetic materials are those in which the geometry of the magnetic sublattice prevents the simultaneous minimization of the energies of different spin-spin interactions.
		One important type of behavior seen in geometrically frustrated magnetic materials is a spin liquid state, in which frustration prevents the onset of long range order, and the spins thus continue to fluctuate down to the lowest temperatures measured.
	www.phys.psu.edu /~schiffer/research (1338 words)

	Unusual material that contracts when heated is giving up its secrets to physicists
		Geometrical frustration sounds like something a high-school math student might feel, but is actually a rich area of research in physics and material science.
		In the case of zirconium tungstate, geometrical frustration comes into play during certain temperature-related vibrations of the compound's crystal lattice structure, the configuration of atomic bonds that holds the atoms together in a crystal.
		On the pure physics side, they seem to provide a new and unusual example of geometrical frustration, which is most often studied in the realm of magnetism and disordered systems such as spin glasses.
	www.eurekalert.org /pub_releases/2004-11/uoc--umt111804.php (828 words)

	Publication abstract / comments @ Penn State Physics (Site not responding. Last check: 2007-11-04)
		Frustration, defined as a competition between interactions such that not all of them can be satisfied, is important in systems ranging from neural networks to structural glasses.
		Geometrical frustration, which arises from the topology of a well-ordered structure rather than from disorder, has recently become a topic of considerable interest.
		In particular, geometrical frustration among spins in magnetic materials can lead to exotic low-temperature states, including 'spin ice', in which the local moments mimic the frustration of hydrogen ion positions in frozen water.
	www.phys.psu.edu /shared/display_abstract.html?pub_id=5802 (232 words)

	Geometrical frustration - Wikipedia, the free encyclopedia
		Geometrical frustration is a phenomenon in condensed matter physics in which the geometrical properties of the atomic lattice forbid the existence of a unique ground state, resulting in a nonzero residual entropy.
		The most important consequence of this is that the entropy of the system does not go to zero at absolute zero.
		An example of a geometrically frustrated material is ordinary water ice, which has a residual entropy of around 3.40 J/K/mole.
	en.wikipedia.org /wiki/Geometrical_frustration (105 words)

	Geometrical frustration in magnetic systems (Site not responding. Last check: 2007-11-04)
		Geometrical frustration is the inabiblity for a system to find a unique ground state due of its geometry.
		The archetypal geometrically frustrated system is based on antiferromagnetically spins located at the vertices of a triangle.
		An interpretation for this peculiar behavior is provided by the presence of a gap in the magnetic excitation spectrum which is linear in temperature [4].
	www-drfmc.cea.fr /Images/Pisp/pdalmas/frustration_general.html (282 words)

	Publisher description for Library of Congress control number 98039488
		This book shows how the concept of geometrical frustration can be used to elucidate the structure and properties of non-periodic materials such as metallic glasses, quasicrystals, amorphous semiconductors and complex liquid crystals.
		Geometric frustration is introduced through examples and idealised models, leading to a consideration of how the concept can be used to identify ordered and defective regions in real materials.
		The text considers geometrical frustration at different scales in many types of materials and structures, including metals, amorphous solids, liquid crystals, amphiphiles, cholisteric systems, polymers, phospholipid membranes, atomic clusters, and quasicrystals.
	www.loc.gov /catdir/description/cam029/98039488.html (220 words)

	Spin glass - Wikipedia, the free encyclopedia
		A spin glass is a disordered material exhibiting high magnetic frustration.
		The origin of the behavior can be either a disordered structure (such as that of a conventional, chemical glass) or a disordered magnetic doping in an otherwise regular structure.
		Frustration refers to the inability of the system to remain in a single lowest energy state (the ground state).
	en.wikipedia.org /wiki/Spin_glass (635 words)

	Distinguished Bell Labs scientist joining Los Alamos
		"Geometrical frustration" refers to a phenomenon in which magnets, or other materials, are "frustrated" when they are forced to settle into a single state.
		A typical "frustrated" material will want to settle in many different states, for instance as it cools down from the temperature at which the solid forms.
		For example, Ramirez recently found several of the hallmarks of geometrical frustration in a material that undergoes negative thermal expansion, meaning that it expands (rather than shrinks) as it is cooled.
	www.lanl.gov /news/releases/archive/00-137.shtml (742 words)

	MATERIALS SCIENCE: ON ELECTRON GEOMETRICAL FRUSTRATION
		1) For electrons on a triangular lattice, the concept of "geometrical frustration" in the face of strong electric (Coulomb) mutual repulsion is a crucial, decisive factor that shapes their behavior.
		On a triangular lattice, however, the geometric arrangement frustrates such ideal regularity.
		The susceptibility resembles that of an insulator that is frustrated from attaining the ordered Neel state as described above.
	scienceweek.com /2004/sc041029-2.htm (1491 words)

	[No title] (Site not responding. Last check: 2007-11-04)
		Using inelastic neutron scattering, we have studied the effects of geometrical frustration in insulating and metallic spinels, AB, where the B sites form a lattice of corner-sharing tetrahedra.
		Geometrical frustration leads to macroscopic degeneracies and qualitatively new states of matter.
		The emergence of composite local spin entities suggests an organizing principle for frustrated systems such that interacting degrees of freedom combine to form rigid clusters if macroscopic condensation is not possible.
	www.nist.gov /sigmaxi/Posters03/park_abstract.html (207 words)

	Session N25 - Geometrical Frustration III. (via CobWeb/3.1 planetlab1.netlab.uky.edu) (Site not responding. Last check: 2007-11-04)
		We have observed a novel weakly dispersive ``zero-energy mode'', which is a consequence of the geometrical frustration.
		Magnetic interactions on geometrically frustrated lattices have been a subject of recent experimental and theoretical studies.
		Frustration effects should be present, but do not yield significant irreversibilities.
	flux.aps.org.cob-web.org:8888 /meetings/YR04/MAR04/baps/abs/S5050.html (1887 words)

	G1
		We have studied a model with geometrical frustration which presents some of the glass-forming systems characteristic properties.
		In this model the variables, from which disorder and frustration originate, are quenched.
		The study of time dependent Ginzburg Landau model showed that in particular initial conditions the short times evolution is well described by a mean field solution, that presents a growing exponent z=1/4, while at long times a crossover to a behavior with an exponent z=1/3 is present.
	www.na.infn.it /infm/g1_pag_1_di_1_eng.htm (157 words)

	cobaltate
		However, for electrons living on a triangular lattice, the concept of “geometrical frustration” in the face of strong Coulomb mutual repulsion is a crucial, decisive factor that shapes their behavior (Fig.
		On the triangular lattice, however, geometric frustration precludes such ideal regularity.
		Apparently, with half of the sites occupied by holes, the system has found a new way to accommodate both the strong Coulomb forces and geometric frustration by firmly localizing the holes (so they lose their ability to carry a current).
	www.princeton.edu /~npo/cobaltate.html (1080 words)

	[No title] (Site not responding. Last check: 2007-11-04)
		in Room 1400A BPS Title: "Geometrical Frustration in Solids" Speaker: Arthur P. Ramirez Los Alamos National Laboratory Abstract: When the symmetry of an order parameter is incompatible with the symmetry of the lattice, the ground state will be highly degenerate.
		We will discuss examples of such geometrically frustrated systems in solids and the new physics that results from strong interactions.
		Examples include spin ice, frustrated soft modes for negative thermal expansion,and pattern formation such as nanotubule variants of liposomes.
	www.pa.msu.edu /seminars/colloquium_2003_Spring/abstract-20030123.txt (101 words)

	Geometrical frustration in 2D optical patterns
		In the case of 2D optical patterns, frustration comes from the interplay between the physical constraints (light-matter interaction) and the geometrical constraints (cavity length and structure).
		For small diffusion and close to threshold, the system is forced to fulfill the geometrical constraints giving rise to a phase dynamics of quasicrystals.
		By means of a geometrical argument, we show that the spatial distribution of domains is related to the symmetry imposed by the geometrical constraint and that the domain borders are disinclination defects.
	www.edpsciences.org /articles/epjd/abs/2000/10/d9784/d9784.html (214 words)

	Souchkov
		Geometrically frustrated magnets can resist magnetic ordering and remain in a strongly correlated paramagnetic state well below the Curie-Weiss temperature.
		, an excellent realization of the Heisenberg antiferromagnet on the pyrochlore network, a lattice distortion relieves the geometrical frustration through a spin-Peierls-like phase transition at Tc=12.5 K with a lowering of the symmetry from cubic to tetragonal.
		Conversely, spin correlations strongly influence the elastic properties of a frustrated magnet.
	www.physics.umd.edu /cmo/people/andrei/Souchkov.htm (557 words)

	Print the story (Site not responding. Last check: 2007-11-04)
		Spin liquids are found in several magnetic materials, including high-temperature superconducting materials, however Gardner studies this exotic magnetic state in materials that exhibit geometrical frustration.
		This occurs when the geometry of the material’s atomic lattice and the magnetic interactions within the material are incompatible.
		This technique uses neutrons to measure the slow motions of atoms, molecules, and magnetic spins on very short timescales — as small as nanoseconds (billionths of a second) and even picoseconds (trillionths of a second).
	www.physorg.com /printnews.php?newsid=11715 (516 words)

	Superconductor Week - Industry News Releases
		Batista proposed a theoretical explanation for this strange behavior: It may be due to an effect called ''geometrical frustration.'' In the crystal structure of barium copper silicate, individual copper atoms in the silicate layers are not stacked directly above each other, but instead, are shifted over in each layer in zigzag fashion.
		Near the critical point, the quantum behavior of the spins in such a layered arrangement may ''frustrate'' one layer from influencing neighboring layers.
		The experimental techniques Sebastian and researchers used to show this effect allowed them to tune high magnetic fields at the lowest experimentally accessible temperatures to precisely access the immediate vicinity of the quantum critical point and explore new physics.
	www.superconductorweek.com /pr/0506hhp/stan1.htm (1304 words)

	Correlations in Arrays of Superconducting Rings
		Regular arrays of such rings may thus be expected to exhibit effects of lattice geometry and geometrical frustration.
		The triangular and Kagome lattices have triplets of rings which lead to geometrical frustration with antiferromagnetic spins.
		For a superconducting ring, the current-vs-flux relationship and the energy are periodic in the applied flux, with period
	www.physics.colostate.edu /groups/fieldgroup/Rings.html (559 words)

	Dynamics of RNase-A and S-Protein: A Molecular Dynamics Simulation of the Transition Toward a Folding Intermediate -- ...
		Frustration, be it energetic or geometric (Sadoc and Mosseri,
		properties of the hydrophobic core of a protein is its geometrical
		The interplay between protein dynamics and frustration of non-bonded interactions as revealed by molecular dynamics simulations.
	www.biophysj.org /cgi/content/full/85/4/2633 (4106 words)

	Artificial /`spin ice/' in a geometrically frustrated lattice of nanoscale ferromagnetic islands: Nature (Site not responding. Last check: 2007-11-04)
		Artificial /`spin ice/' in a geometrically frustrated lattice of nanoscale ferromagnetic islands: Nature
		Artificial 'spin ice' in a geometrically frustrated lattice of nanoscale ferromagnetic islands
		In particular, geometrical frustration among spins in magnetic materials can lead to exotic low-temperature states
	www.nature.com /nature/journal/v439/n7074/abs/nature04447.html (315 words)

	LiveScience.com - Strange Shrinking Material
		Now Schlesinger and his colleagues think they have found the reason for zirconium tungstate’s stability in something called geometrical frustration.
		When the temperature rises, these geometric figures squeeze together, but they do not match up very well.
		If there were no geometric frustration, zirconium tungstate would eventually rearrange itself and behave like most other materials.
	www.livescience.com /technology/041215_unusual_material.html (525 words)

	Effects of Geometrical Frustration in the Hubbard Model (via CobWeb/3.1 planetlab1.netlab.uky.edu) (Site not responding. Last check: 2007-11-04)
		We have studied the effects of geometrical frustration in the Hubbard model defined on a two-dimensional lattice with adjustable degrees of frustration.
		Exact diagonalization techniques are applied to an eight-site cluster with periodic boundary conditions.
		Ground-state properties are calculated and analyzed to gain insight into the role of the geometrical frustration in determining the electronic and magnetic structures of the system.
	flux.aps.org.cob-web.org:8888 /meetings/YR98/BAPSMAR98/abs/S1875111.html (103 words)

	UA Physics Department - Colloquium Series
		Abstract: Geometrical Frustration occurs when an order parameter symmetry is incompatible with the spatial symmetry of the lattice.
		The simplest example is that of antiferromagnetic Ising spins on a triangular lattice.
		We will present a materials classification of this phenomenon for magnetic systems, and show how this condition can lead to new magnetic ground states such as spin ice and spin liquid.
	www.physics.arizona.edu /physics/colloquium/dept.html (761 words)

	Diffuse Workshop Abstract (Site not responding. Last check: 2007-11-04)
		Frustration and Random Fields in Triangular Lattice Antiferromagnets
		Geometrical frustration manifests in these materials through the appearance of an unusual long range ordered state in CsCoBr
		Copyright © 2003 Ray Osborn and Stephan Rosenkranz.
	www.neutron.anl.gov /diffuse/program/0008 (109 words)

	DEMOCRITOS - Freezing and large time scales induced by geometrical frustration (Site not responding. Last check: 2007-11-04)
		DEMOCRITOS - Freezing and large time scales induced by geometrical frustration
		Freezing and large time scales induced by geometrical frustration
		We investigate the properties of an effective Hamiltonian with competing interactions involving spin and chirality variables, relevant for the description of the trimerized version of the spin-1/2 kagome antiferromagnet.
	www.democritos.it /publications/abstracts/abstract_239.html (130 words)

	WEB_FRUSTRATION
		Nine appendices give all necessary background on geometry, symmetry and tilings.
		The text considers geometrical frustration at different scales in many types of materials and structures, including metals, amorphous solids, liquid crystals, amphiphiles, cholesteric systems, polymers, phospholipid membranes, atomic clusters, and quasicrystals.
		[51] J.F. SADOC and J. "Frustration in bilayers and topologies of liquid crystals of amphilic molecules"
	www.lps.u-psud.fr /Collectif/gr_23/themes/jfsadocBooks.htm (1567 words)

	Freezing Magnets With Magnets
		His talk will take place at 3:42 pm on March 13, in room 307 of the Baltimore Convention Center.
		Abbreviated Tb2Ti2O7, this material remains in a spin liquid state at extreme low temperatures, but begins to crystallize under extremely high pressure (100,000 times atmospheric pressure) and now, as Gardner and his group have discovered, under magnetic fields.
		The research was funded by the Office of Basic Energy Sciences within the U.S. Department of Energy's Office of Science.
	www.bnl.gov /bnlweb/pubaf/pr/PR_display.asp?prID=06-24 (698 words)

	1.1 Antiferromagnetic spin systems without Néel order (Site not responding. Last check: 2007-11-04)
		But recently, several theoretical situations have been proposed, in which an antiferromagnetic spin system prefers a many-body singlet ground state, rather than the Néel state.
		These situations include low dimensionality and/or geometrical frustration of the spins, so that the conventional Néel order is suppressed.
		Amazingly, several materials have been discovered which may realize the theoretical situations.
	musr.physics.ubc.ca /theses/Kojima/node3.html (639 words)

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