Ph.D. Thesis --- Peter Matus

Peter Matus

Description

• dissertation - matière potentielle : the
• dissertation - matière potentielle : bears

INFLUENCE OF LOCAL C60 ORIENTATION ON ELECTRONIC PROPERTIES OF A3C60 COMPOUNDS Ph.D. Thesis PÉTER MATUS Supervisors HENRI ALLOUL GYÖRGY KRIZA directeur de recherche scientific advisor Laboratoire de Physique Research Institute for Solid State Physics des Solides, Université Paris-Sud and Optics, Hungarian Academy of Sciences Orsay, France Budapest, Hungary RESEARCH INSTITUTE FOR SOLID STATE PHYSICS AND OPTICS of the Hungarian Academy of Sciences BUDAPEST 2006

• relaxation rate
• interactions between
• interactions between nuclear
• sodium spin lattice
• line splits
• na nmr
• local c60
• spin
• spins

Sujets

• Balázs
• Brouet
• Williams

Informations

• Publié par: onji
• Nombre de lectures: 44
• Poids de l'ouvrage: 1 Mo

Extrait

INFLUENCEOFLOCALC ORIENTATION60
ONELECTRONICPROPERTIESOFA C3 60
COMPOUNDS
Ph.D.Thesis
PÉTERMATUS
Supervisors
HENRIALLOUL GYÖRGYKRIZA
directeurderecherche scientificadvisor
LaboratoiredePhysique ResearchInstituteforSolidStatePhysics
desSolides,UniversitéParis-Sud andOptics,HungarianAcademyofSciences
Orsay,France Budapest,Hungary
RESEARCHINSTITUTEFORSOLIDSTATEPHYSICSANDOPTICS
oftheHungarianAcademyofSciences
BUDAPEST
2006SincewhatmaybeknownGodisplaintothem,
becauseGodhasmadeitplaintothem.
Forsincethecreationoftheworld
God’sinvisiblequalities
—Hiseternalpoweranddivinenature—
havebeenclearlyseen,
beingunderstoodfromwhathasbeenmade.
ROMANS 1,19–20Contents
Contents i
ListofFigures iii
ListofTables v
Acknowledgement vi
Abstract viii
Kivonat ix
1 Introduction 1
2 Theworldoffullerenes 3
2.1 ThebuckminsterfullereneC . . . . . . . . . . . . . . . . . . . . . . 360
2.1.1 ThemolecularstructureofC fullerene . . . . . . . . . . . . 360
2.1.2 Fullerite,thecrystallineformoffullerene . . . . . . . . . . . 5
2.1.3 Fullerenecompounds . . . . . . . . . . . . . . . . . . . . . . 9
2.2 Alkalifulleridesalts. . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2.1 A C superconductors . . . . . . . . . . . . . . . . . . . . . 113 60
3 Nuclearmagneticresonancespectroscopy 15
3.1 PhysicalbackgroundofNMR . . . . . . . . . . . . . . . . . . . . . . 16
3.1.1 Nuclearspintransition . . . . . . . . . . . . . . . . . . . . . . 16
3.1.2 Nuclearmagnetization . . . . . . . . . . . . . . . . . . . . . . 17
3.1.3 Larmorprecession . . . . . . . . . . . . . . . . . . . . . . . . 17
3.1.4 Relaxationalprocesses . . . . . . . . . . . . . . . . . . . . . . 19
3.2 Pulsesequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2.1 Spin-echo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
3.2.2 Measurementofthespin-latticerelaxationtime . . . . . . . 23
3.3 InteractionsinNMRspectroscopy . . . . . . . . . . . . . . . . . . . 24
3.3.1 Interactionsbetweennuclearspins . . . . . . . . . . . . . . . 25
3.3.2 Quadrupolarinteraction . . . . . . . . . . . . . . . . . . . . . 26
3.3.3 Interactionsbetweenelectronsandnuclearspins . . . . . . . 26
3.4 Spin-echodoubleresonance . . . . . . . . . . . . . . . . . . . . . . . 28
iCONTENTS ii
4 Experimental 30
4.1 Samplepreparationandcharacterization . . . . . . . . . . . . . . . 30
4.2 NMRapparatus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
4.3 Measurementsetup,dataprocessing . . . . . . . . . . . . . . . . . . 35
4.3.1 SEDOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
5 Results 40
5.1 LinesplittingintheNMRspectra . . . . . . . . . . . . . . . . . . . . 40
235.1.1 NaNMRspectraofNa CsC . . . . . . . . . . . . . . . . . 402 60
235.1.2 NaNMRspectraofNa RbC andNa KC compounds . 422 60 2 60
235.1.3 NaNMRlinewidthinNa CsC . . . . . . . . . . . . . . . 452 60
05.2 IsthedetectedT peakintrinsic? . . . . . . . . . . . . . . . . . . . . 46
5.2.1 NMRlineshiftsinNa CsC . . . . . . . . . . . . . . . . . . 462 60
5.2.2 Spin-echodoubleresonanceexperiments . . . . . . . . . . . 47
0 135.3 ComparisonofT spectralweightand Clinewidth . . . . . . . . 49
5.4 Relaxationrates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
5.4.1 Spin-spinrelaxation . . . . . . . . . . . . . . . . . . . . . . . 50
5.4.2 Spin-latticerelaxation . . . . . . . . . . . . . . . . . . . . . . 50
6 Discussion 52
6.1 Orientationalorderingtransition . . . . . . . . . . . . . . . . . . . . 52
6.2 Tetrahedrallinesplitting . . . . . . . . . . . . . . . . . . . . . . . . . 54
6.3 Influenceofquadrupolarinteractiononthelineshape . . . . . . . . 55
6.4 SodiumsiteexchangeduetoC reorientations . . . . . . . . . . . . 5760
236.4.1 NaNMRspectrum . . . . . . . . . . . . . . . . . . . . . . . 57
6.4.2 Spin-spinrelaxation . . . . . . . . . . . . . . . . . . . . . . . 59
6.4.3 Spin-latticerelaxation . . . . . . . . . . . . . . . . . . . . . . 61
6.4.4 Dynamicalcrossover . . . . . . . . . . . . . . . . . . . . . . . 63
6.5 TheinfluenceoflibrationsonT relaxationrates . . . . . . . . . . . 651
06.6 T–T splittingduetoC orientationalenvironments . . . . . . . . 6960
6.6.1 TheoriginofsplittinginNa AC . . . . . . . . . . . . . . . 692 60
06.6.2 T–T probleminA C withmerohedraldisorderrevisited . 733 60
7 Conclusion 78
Bibliography 80
Ownpublications 87ListofFigures
2.1 StructureofaC molecule . . . . . . . . . . . . . . . . . . . . . . . 460
2.2 C bondlengths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 560
2.3 ElectronicstructureofC andbandstructureofK C . . . . . . . 660 3 60
2.4 Twostandardorientations: merohedraldisorder . . . . . . . . . . . 7
2.5 Nearestneighborfullereneconfigurations . . . . . . . . . . . . . . . 8
2.6 Twoexamplesoffullerenecompounds . . . . . . . . . . . . . . . . . 9
2.7 InterstitialsitesinfcchostlatticeofC . . . . . . . . . . . . . . . . 1060
2.8 StructureofalkaliC compounds . . . . . . . . . . . . . . . . . . . 1160
2.9 Latticeconstantdependenceofsupercond. transitiontemperature . 12
02.10 FirstobservationofT–T splitting . . . . . . . . . . . . . . . . . . . . 13
3.1 Precessionofmagneticmomentin B rffield(rotatingframe). . . . 181
3.2 Precessionofmagneticmomentin x–yplanein B field . . . . . . . 180
3.3 Relaxationalprocesses . . . . . . . . . . . . . . . . . . . . . . . . . . 20
3.4 Spin-echopulsesequence . . . . . . . . . . . . . . . . . . . . . . . . 23
3.5 Saturationrecoverypulsesequence . . . . . . . . . . . . . . . . . . . 24
3.6 Inversionrecoverypulsesequence . . . . . . . . . . . . . . . . . . . 24
3.7 SEDORpulsesequence . . . . . . . . . . . . . . . . . . . . . . . . . . 28
4.1 Na CsC magnetizationbySQUID . . . . . . . . . . . . . . . . . . 312 60
4.2 SamplecharacterizationbyusingNMRspectra . . . . . . . . . . . . 32
4.3 Blockdiagramofhome-builtNMRspectrometer . . . . . . . . . . . 33
4.4 NMRprobehead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
4.5 FIDandNMRspectrumat100K . . . . . . . . . . . . . . . . . . . . 36
4.6 Decayofreducedmagnetizationin T measurement . . . . . . . . . 371
4.7 Decayoftransversemagnetizationin T measurement. . . . . . . . 382
235.1 NaNMRspectraofNa CsC . . . . . . . . . . . . . . . . . . . . . 412 60
235.2 NaNMRspectraofdifferentNa AC salts . . . . . . . . . . . . . 432 60
5.3 NMRspectratakenbydifferentcoolingrates . . . . . . . . . . . . . 44
235.4 FWHMlinewidthof NaNMRspectruminNa CsC . . . . . . . 452 60
235.5 Temperaturedependenceof NaNMRlineshiftsinNa CsC . . 462 60
5.6 SEDORfractionsat80K . . . . . . . . . . . . . . . . . . . . . . . . . 47
0 135.7 TemperaturedependenceofT spectralratioand Clinewidth . . 49
235.8 Temperaturedependenceof Naspin-spinrelaxationrate . . . . . 50
iiiLISTOFFIGURES iv
5.9 Temperaturedependenceofsodium1/(T T)relaxationrate . . . . 511
236.1 NaNMRspectrumofNa CsC fromSaitoetal. . . . . . . . . . . 532 60
6.2 DisplacementofsodiumionsinNa AC compounds . . . . . . . . 542 60
236.3 Naspectrumtogetherwithlinefitsat100K . . . . . . . . . . . . . 55
6.4 MeasuredandsimulatedNMRspectraofNa CsC . . . . . . . . . 582 60
6.5 Spin-spinrelaxationratewithfit . . . . . . . . . . . . . . . . . . . . 60
6.6 Arrheniusplotofspin-latticerelaxationrate . . . . . . . . . . . . . . 61
6.7 Spin-latticerelaxationrateswithfits . . . . . . . . . . . . . . . . . . 63
1/26.8 1/(T T) displayedasafunctionoflineshift . . . . . . . . . . . . 661
6.9 MeasuredlineshiftsfittedwithEinsteinmodel . . . . . . . . . . . . 68
+6.10 LocalC orderaroundtetrahedralintersticesfromNa ions . . . . 7160
6.11 Relativedeviationofthesecondmoment . . . . . . . . . . . . . . . 75
¯6.12 FullereneconfigurationsaroundaTsiteinthe Fm3mstructure . . . 76ListofTables
6.1 Exchangeparameters . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
6.2 LocalC configurations . . . . . . . . . . . . . . . . . . . . . . . . . 7260
6.3 Relativedeviationofthesecondmoment . . . . . . . . . . . . . . . 75
¯6.4 C configurationsaroundatetrahedralsitein Fm3mstucture. . . . 7660
vAcknowledgement
Although this dissertation bears my name on the front, if it were not for the
selflessnessofahostofpeopleIwouldnothavebeenabletoreachthispointof
mylifeonmyown. Letmeexplicitlyrefertosomeofthemhereandnowwitha
remarkthatthelistwillnotbeexhaustive.
FirstandforemostIwouldliketoexpressmyextraordinarygratitudeforthe
patience, counsel and leadership of my two mentors, György Kriza and Henri
Alloul. Their ability to ask the right question at the right time and to verbalize
theirthoughtswithprofoundprecisionchangedmeinnumerousways.
I am very grateful for the collaboration with László Forró and his group
in Lausanne who provided us high quality samples prepared by Slaven Garaj.
Theircontributionwasindispensableforthisthesis.
Consultationswithx-rayandneutronscatteringexpertshavebeenparticular-
lyusefulwhensolvingsomeoftheproblemspointedoutinthethesis. Fortheir
willingness to help my gratefulness goes to Gábor Oszlányi, Kosmas Prassides
and Roger Moret. The comments and remarks on NMR by Kálmán Tompa,
AndrásJánossyandCharlesSlichteralwaysencompassedmorethanIexpected
butneverlessthanwhattheproblemdemanded.
I am very grateful for the many ways Gyöngyi Pergerné Klupp