Europhys. Lett.
Volume 47, Number 2, July 1999
Page(s) 247 - 253
Section Condensed matter: electronic structure, electrical, magnetic and optical properties
Published online 01 September 2002
DOI: 10.1209/epl/i1999-00379-x

Europhys. Lett, 47 (2), pp. 247-253 (1999)

Dynamical magnetic correlations in the Kondo insulator $\rm YbB_{12}$

A. Yaouanc 1, P. Dalmas de Réotier 1, P. Bonville 2, G. Lebras 2
P. C. M. Gubbens 3, A. M. Mulders 3 and S. Kunii 4

1 Commissariat à l'Energie Atomique, Département de Recherche Fondamentale sur la
Matière Condensée, Service de Physique Statistique, Magnétisme et Supraconductivité
F-38054 Grenoble Cedex 9, France
2 Commissariat à l'Energie Atomique, Département de Recherche sur l'Etat Condensé,
les Atomes et les Molécules - F-91191 Gif-sur-Yvette, France
3 Interfacultair Reactor Instituut, Delft University of Technology
2629 JB Delft, The Netherlands
4 Department of Physics, Faculty of Science, Tohoku University
Sendai 980, Japan

(received 15 February 1999; accepted in final form 12 May 1999)

PACS. 75.20Hr - Local moment in compounds and alloys; Kondo effect, valence fluctuations, heavy fermions.
PACS. 71.28+d - Narrow-band systems; intermediate-valence solids.
PACS. 76.75+i - Muon spin rotation and relaxation.


Positive muon spectroscopy ($\mu$SR) and 170Yb Mössbauer absorption measurements have been performed in the cubic Kondo insulator YbB12 down to the 50mK temperature range. We observe a paramagnetic fluctuation mode at low temperature, with a weak moment amplitude ($\approx 10^{-2}$ $\mu_{\rm B}$) and a slow fluctuation frequency ($\approx$ 60 MHz) which remains constant between 0.04K and 4.2K. No indication of a magnetic phase transition is found down to 0.04 K.


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