Etude de systèmes frustrés par diffusion neutronique : Pr2Zr2o7 et Tb2Ti2o7 sont-ils des glaces de spin quantiques ?

Abstract : This work is the neutron scattering study of the pyrochlores Tb2Ti2O7 and Pr2Zr2O7. These compounds where magnetic ions are Non-Kramers ions are expected to be quantum spin ices. In Pr2Zr2O7, the study of the elastic and inelastic response together with the study of the magnetic structures in applied magnetic field lead to the conclusion that the magnetic ground state is a mixing of the wave functions of the crystal-field ground state doublet because of quadrupolar terms in the Hamiltonian. These terms would originate from a coupling to the lattice. Using the mean-field approximation, a model based on a local structural distortion reproduces quite well our measurements. Despite strong differences with Pr2Zr2O7, our measurements provide evidence for a similar mechanism in Tb2Ti2O7. Again, this would be caused by multipolar terms in the Hamiltonian reflecting a strong coupling of the magnetic moments to the lattice. Then, these pyrochlores would not be quantum spin ices. Instead, the extreme sensibility to the environment characteristic of the Non-Kramers ions would lead to these fluctuations. Our measurements of samples slightly off-stoichiometry emphases the strong reactivity of the magnetic behavior of these compounds.
Document type :
Theses
Complete list of metadatas

Cited literature [131 references]  Display  Hide  Download

https://tel.archives-ouvertes.fr/tel-01270680
Contributor : Abes Star <>
Submitted on : Monday, February 8, 2016 - 12:58:06 PM
Last modification on : Thursday, February 7, 2019 - 1:33:40 AM
Long-term archiving on: Saturday, November 12, 2016 - 1:30:08 PM

File

2015PA066370.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : tel-01270680, version 1

Citation

Solène Guitteny. Etude de systèmes frustrés par diffusion neutronique : Pr2Zr2o7 et Tb2Ti2o7 sont-ils des glaces de spin quantiques ?. Matière Condensée [cond-mat]. Université Pierre et Marie Curie - Paris VI, 2015. Français. ⟨NNT : 2015PA066370⟩. ⟨tel-01270680⟩

Share

Metrics

Record views

767

Files downloads

993