Dynamical magnetic correlations in the Kondo insulator

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: 12 May 1999

Abstract

Positive muon spectroscopy (μSR) and ¹⁷⁰Yb Mössbauer absorption measurements have been performed in the cubic Kondo insulator YbB₁₂ down to the 50 mK temperature range. We observe a paramagnetic fluctuation mode at low temperature, with a weak moment amplitude ( ) and a slow fluctuation frequency (≈ 60 MHz) which remains constant between 0.04 K and 4.2 K. No indication of a magnetic phase transition is found down to 0.04 K.