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Digital archive of theses discussed at the University of Pisa

 

Thesis etd-02162006-130735


Thesis type
Tesi di dottorato di ricerca
Author
Ippolito, Daniele
email address
daniele.ippolito@poste.it
URN
etd-02162006-130735
Thesis title
Jahn-Teller Effect on Rare Earth Dioxides
Academic discipline
FIS/01
Course of study
FISICA
Supervisors
relatore Prof.ssa Martinelli, Liana
Keywords
  • electron-phonon interaction
  • Jahn-Teller effect
  • PrO2
  • rare earth dioxides
  • UO2
  • vibronic coupling
Graduation session start date
22/03/2006
Availability
Full
Summary
A number of experimental facts found in PrO2 and UO2, such as anomalies in the magnetic excitations spectrum, the reduction of the ordered magnetic moment for T < TN and the distortion of the oxygen cage are interpreted as consequences of electron-phonon coupling and cooperative effects. A simple microscopic model including crystal field, magnetic exchange interaction and cooperative dynamical Jahn-Teller coupling is here proposed. A coupling to phonons of trigonal symmetry is found appropriate to describe the experimental results. A single-centre model can explain the reduction of the ordered magnetic moment and also the main features of the differential cross section; however, in PrO2, a cooperative interaction is necessary to interpret the observed distortion of the oxygen cage and the observed splitting of the ground state into two doublets in the paramagnetic phase.
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