Quantum spin dynamics

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A new mechanism for electron spin echo envelope modulation

(2004)

Authors:

John JL Morton, Alexei M Tyryshkin, Arzhang Ardavan, Kyriakos Porfyrakis, Stephen A Lyon, G Andrew D Briggs
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Fermiology of new charge-transfer salts, β″-(BEDT-TTF) 4[(H3O)M(C2O4)3]-solvent where M = Ga, Cr and Fe

Journal De Physique. IV : JP 114 (2004) 205-209

Authors:

AI Coldea, AF Bangura, A Ardavan, J Singleton, A Akutsu-Sato, H Akutsu, SS Turner, P Day

Abstract:

We report high-field magnetotransport measurements on β″-(BEDT- TTF)4[(H3O)M(C2O4) 3]· solvent, where M=Ga3+, Cr3+ and Fe3+ and solvent=C5H5N. In spite of their differing transition metal-ions, M, the three compounds exhibit similar magnetic quantum oscillation spectra superimposed on a positive magnetoresistance. At least four independent quantum oscillation frequencies have been identified, corresponding to two different hole and electron pockets of the Fermi surface which follow the rules of a compensated metal. Observation of the small pockets could be the result of the Fermi surface reconstruction induced by a possible density wave. The effective masses are very similar for different samples and for different pockets range between meff ≈ 0.5-1.1 me whereas the Dingle temperatures varies between TD ≈ 1.4-4 K. At low temperature, the longitudinal magnetoresistance violates Kohler's rule, suggesting that the interlayer transport in these quasi-2D systems cannot be related to a single scattering time and that the disorder plays an important role. © EDP Sciences.
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The effect of magnetic ions and disorder on superconducting β″-(BEDT-TTF)4[(H3O)M(C2O 4)3]· C6H5NO2 salts, where M = Ga and Cr

Journal De Physique. IV : JP 114 (2004) 285-287

Authors:

AF Bangura, AI Coldea, A Ardavan, J Singleton, A Akutsu-Sato, H Akutsu, P Day

Abstract:

We report magnetotransport measurements performed in magnetic fields of up to 33 T and at low temperatures (0.45 K
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Experimental observation of nonspherlcally-decaying radiation from a rotating superluminal source

Journal of Applied Physics 96:8 (2004) 4614-4631

Authors:

A Ardavan, W Hayes, J Singleton, H Ardavan, J Fopma, D Halliday

Abstract:

An experimental implementation of an oscillating, superluminal polarization current distribution that undergoes centripetal acceleration was constructed and tested. The emission from the experimental machine was found to be tightly beamed in both the azimuthal and polar directions. It was found that the beaming is frequency independent and has a sharply defined and unchanging geometry determined only by the speed and path of the moving distribution pattern. The intensity of the radiation at these angles was observed to decline more slowly with increasing distance from the source than would the emission from a conventional antenna.
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Ordering and interaction of molecules encapsulated in carbon nanotubes

MATER SCI TECH-LOND 20:8 (2004) 969-974

Authors:

AN Khlobystov, K Porfyrakis, DA Britz, M Kanai, R Scipioni, SG Lyapin, JG Wiltshire, A Ardavan, D Nguyen-Manh, RJ Nicholas, DG Pettifor, TJS Dennis, GAD Briggs

Abstract:

A clear understanding of the interactions between the building blocks of self-assembled molecular materials is essential for rational design of functional nanostructures. Intermolecular interactions have been investigated for three different classes of fullerenes in single-walled carbon nanotubes (SWNTs); van der Waals molecule -molecule and molecule-SWNT interactions control the geometry of the molecular arrays inside nanotubes; electrostatic intermolecular forces influence the alignment of polar endohedral fullerenes M@C-82; and hydrogen bonding between functionalised fullerenes has a significant effect on the selectivity of insertion of functionalised fullerenes into SWNTs.
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