Berlin 2005 – wissenschaftliches Programm
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M: Metallphysik
M 19: Nanoskalige Materialien II
M 19.2: Vortrag
Samstag, 5. März 2005, 11:15–11:30, TU H111
Grain size effect on the temperature dependence of the electric field gradient — •X.M. Li, Z.Q. Guan, H. Wolf, and Th. Wichert — Technische Physik, Universität des Saarlandes, D-66123 Saarbrücken
In many non-cubic bulk metals the temperature dependence of the electric field gradient (EFG) can be described by a T3/2 dependence. Some theoretical models considering the electronic structure and the influence of phonons have been presented in the literature in order to explain this relation. Since it is expected that a reduction of the grain size to nanometer scale affects the electronic structure as well as the phonon spectrum, the temperature dependence of EFG might be changed in nanocrystalline non-cubic metals as well.
Nanocrystalline Indium has been prepared with different particle sizes by the method of electrochemical deposition. The temperature dependence of the EFG as a function of different particles sizes (11 nm, 12, nm, 27 nm, as determined by TEM) was investigated in the temperature range of 20-300 K using the perturbed γγ-angular correlation technique (PAC).
The data show that the temperature dependence of the EFG in nanokristalline In still follows a T3/2 dependence. However, the coupling constant νQ(0), extrapolated to zero temperature, and the slope B, quantifying the T3/2, relation are changed compared to the respective values of the bulk material. Both parameters obviously depend on the grain size of nanocrystalline In. From the analysis of the data it is concluded that the observed changes of the EFG can completely be explained by changes of the lattice constants.
Supported by the DFG within the SFB 277.