Neutron Larmor diffraction investigation of the rare-earth pyrochlores R2Ti2O7 ( R=Tb , Dy, Ho)
| Autor: | Thomas Keller, M. Ruminy, Tom Fennell, Felix Groitl |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
Physics
education.field_of_study Condensed matter physics Phonon Population Charge (physics) 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Thermal expansion Lattice constant Negative thermal expansion Excited state 0103 physical sciences 010306 general physics 0210 nano-technology education Spin-½ |
| Zdroj: | Physical Review B. 94 |
| ISSN: | 2469-9969 2469-9950 |
| Popis: | In this work, we present a neutron Larmor diffraction study of the rare-earth pyrochlores ${R}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ with $R=\mathrm{Tb}$, Dy, Ho. We measured the temperature dependence of the lattice parameter with precision ${10}^{\ensuremath{-}5}$, between 0.5 and 300 K in each of the three compounds. The lattice parameter of the spin ices ${\mathrm{Dy}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ and ${\mathrm{Ho}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$ enters into the derivation of the charge of the emergent magnetic monopole excitations suggested to exist in these materials. We found that throughout the range of applicability of the theory of emergent monopoles in the spin ices there will be no renormalization of the monopole charge due to lattice contraction. In ${\mathrm{Tb}}_{2}{\mathrm{Ti}}_{2}{\mathrm{O}}_{7}$, strong magnetoelastic interactions have been reported. We found no sign of the previously reported negative thermal expansion, but did observe anomalies in the thermal expansion that can be correlated with previously observed interactions between phonon and crystal-field excitations. Other features in the thermal expansion of all three compounds can be related to previously observed anomalies of the elastic constants, and explained by the phonon band structure of the rare-earth titanates. The temperature dependence of the lattice strain in all three compounds can be correlated with the thermal population of excited crystal-field levels. |
| Databáze: | OpenAIRE |
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