arXiv subjects

E. S. Clementyev

Publications and source records attributed to E. S. Clementyev.

3 recordsLinked to original sources

arXiv2019

Ab initio study of lattice dynamics of dodecaborides ZrB12 and LuB12

We performed ab initio lattice-dynamics calculations of frame-cluster dodecaborides ZrB12 and LuB12. As a whole, our calculated phonon frequencies and atom-projected density of states are consistent with the results of available first-principles calculations and experimental measurements. So we conclude that the ab initio DFT approach is quite appropriate to study the sufficiently subtle physics of these compounds. Our experiment-independent calculations provide an explicit quantitative confirmation of mixing the eigenvectors of boron and metal vibrations, which was previously observed in experiments.

physics.chem-ph↗

arXiv2004

Yb-Yb correlations and crystal-field effects in the Kondo insulator YbB12 and its solid solutions

We have studied the effect of Lu substitution on the spin dynamics of the Kondo insulator YbB12 to clarify the origin of the spin-gap response previously observed at low temperature in this material. Inelastic neutron spectra have been measured in Yb1-xLuxB12 compounds for four Lu concentrations x = 0, 0.25, 0.90 and 1.0. The data indicate that the disruption of coherence on the Yb sublattice primarily affects the narrow peak structure occurring near 15-20 meV in pure YbB12, whereas the spin gap and the broad magnetic signal around 38 meV remain almost unaffected. It is inferred that the latter features reflect mainly local, single-site processes, and may be reminiscent of the inelastic magnetic response reported for mixed-valence intermetallic compounds. On the other hand, the lower component at 15 meV is most likely due to dynamic short-range magnetic correlations. The crystal-field splitting in YbB12 estimated from the Er3+ transitions measured in a Yb0.9Er0.1B12 sample, has the same order of magnitude as other relevant energy scales of the system and is thus likely to play a role in the form of the magnetic spectral response.

cond-mat.str-el↗

arXiv2001

Collective magnetic excitations in mixed-valence Sm0.83Y0.17S

The magnetic spectral response of black-phase mixed-valence Sm0.83Y0.17S has been measured by inelastic neutron scattering on a single crystal. Two magnetic peaks are observed in the energy range of the Sm2+ spin-orbit transition (25-40 meV). Both of them exhibit significant dispersion along the three main symmetry directions, reminiscent of the spin-orbit exciton branch found in pure divalent SmS. The results can be reproduced by a simple phenomenological model accounting for the existence of sizeable Sm-Sm exchange interactions, and a microscopic mechanism is proposed on the basis of the "local-bound-state" theory developed previously for SmB6.

cond-mat.str-el↗