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

P. A. Alekseev·J. -M. Mignot·K. S. Nemkovski·E. V. Nefeodova·N. Yu. Shitsevalova·Yu. B. Paderno·R. I. Bewley·R. S. Eccleston·E. S. Clementyev·V. N. Lazukov·I. P. Sadikov·N. N. Tiden
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Abstract

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.

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P. A. Alekseev, J. -M. Mignot, K. S. Nemkovski, E. V. Nefeodova, N. Yu. Shitsevalova, Yu. B. Paderno, R. I. Bewley, R. S. Eccleston, E. S. Clementyev, V. N. Lazukov, I. P. Sadikov, N. N. Tiden. 2004-03-08. Yb-Yb correlations and crystal-field effects in the Kondo insulator YbB12 and its solid solutions. https://doi.org/10.1088/0953-8984%2F16%2F15%2F015

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