Two stage pressure-induced Yb valence change in the Hexagonal Laves Phase YbAg$_2$: Investigation by time differential perturbed angular $γ$-$γ$ correlation spectroscopy method and density functional calculations

A. V. Tsvyashchenko; A. N. Nikolaev; D. A. Salamatin; A. Velichkov; A. V. Salamatin; A. P. Novikov; L. N. Fomicheva; F. S. El'kin; A. V. Bibikov; M. G. Kozin; M. Budzynski

doi:10.1103/physrevb.96.245141

arXiv · 1711.02888

Two stage pressure-induced Yb valence change in the Hexagonal Laves Phase YbAg$_2$: Investigation by time differential perturbed angular $γ$-$γ$ correlation spectroscopy method and density functional calculations

A. V. Tsvyashchenko·A. N. Nikolaev·D. A. Salamatin·A. Velichkov·A. V. Salamatin·A. P. Novikov·L. N. Fomicheva·F. S. El'kin·A. V. Bibikov·M. G. Kozin·M. Budzynski

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Abstract

We have studied the C14 hexagonal Laves phase of YbAg$_2$ at normal conditions and under external pressure up to 19 GPa by the time-differential perturbed angular $γ-γ$ correlation spectroscopy (TDPAC) using $^{111}$Cd probe nuclei. Under pressure the valence of Yb undergoes a two stage transition from 2.8 to 3. The two stage scenario is characterized by two distinct quadrupole frequencies of $^{111}$Cd probes in silver sublattice, monotonically increasing with pressure and saturating at 8 and 16 GPa. Our experimental data are compared with the density functional studies of the electron band structure of YbAg$_2$, whose results are used for discussion and interpretation of these experiments. We have found that there are two different electric field gradients at inequivalent silver sites and that $4d$-states of silver participate in metal bonding, allowing for the formation of the hexagonal Laves phase.

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A. V. Tsvyashchenko, A. N. Nikolaev, D. A. Salamatin, A. Velichkov, A. V. Salamatin, A. P. Novikov, L. N. Fomicheva, F. S. El'kin, A. V. Bibikov, M. G. Kozin, M. Budzynski. 2017-11-08. Two stage pressure-induced Yb valence change in the Hexagonal Laves Phase YbAg$_2$: Investigation by time differential perturbed angular $γ$-$γ$ correlation spectroscopy method and density functional calculations. https://doi.org/10.1103/physrevb.96.245141

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