Spin gap in CeFe4Sb12 studied by heat capacity and inelastic neutron scattering

R. Viennois, L. Girard, L. C. Chapon, D. T. Adroja, R. I. Bewley, D. Ravot, Peter. S. Riseborough, and S. Paschen
Phys. Rev. B 76, 174438 – Published 29 November 2007

Abstract

The magnetic properties of the skutterudite compound CeFe4Sb12 have been investigated by heat capacity and inelastic neutron scattering measurements. Heat capacity measurements reveal a broad peak centered at 125K, whose magnitude is much larger than that expected from a Schottky anomaly due to a cubic crystal electric field. At 5K, inelastic neutron scattering experiments clearly show the existence of a broad magnetic peak at 40(3)meV. The absence of quasielastic scattering at this temperature, together with the almost total account of the magnetic signal in the inelastic peak, shows that the excitation has a different origin than a splitting of the electronic levels due to crystal field potential. Instead, we propose a model in which the signal originates from inelastic excitations across two hybridization bands near the Fermi energy, usually referred to as a spin gap. A simple phenomenological two-level model can account for the peak in the specific heat, with a spin-gap energy of 36(2)meV, which is in very good agreement with the inelastic scattering data. Further, at 300K, the inelastic response becomes purely quasielastic, which is in agreement with the theoretical calculations. Interestingly, the spin-gap energy in CeFe4Sb12 exhibits a universal scaling behavior with the Kondo temperature TK. The relation between the spin-gap energy and the associated anomalies in the heat capacity or thermal expansion is discussed for a series of Ce- and Yb-based compounds.

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  • Received 17 May 2007

DOI:https://doi.org/10.1103/PhysRevB.76.174438

©2007 American Physical Society

Authors & Affiliations

R. Viennois1,2,3, L. Girard2, L. C. Chapon4, D. T. Adroja4,*, R. I. Bewley4, D. Ravot2, Peter. S. Riseborough5, and S. Paschen3,6

  • 1DPMC, Université de Genève, 24 Quai Ernest Ansermet, CH-1211 Genève 4, Switzerland
  • 2LPMC, Université Montpellier II, Place Eugène Bataillon, F-34095 Montpellier, France
  • 3Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Strasse 40, D-01185 Dresden, Germany
  • 4ISIS Facility, Rutherford Appleton Laboratory, Chilton Didcot, Oxfordshire OX11 0QX, United Kingdom
  • 5Department of Physics, Temple University, Barton Hall, 1900 North 13th Street, Philadelphia, Pennsylvania 19122, USA
  • 6Department of Solid State Physics, Vienna University of Technology, Wiedner Houptstrasse 8-10, 1040 Vienna, Austria

  • *Author to whom correspondence should be addressed; d.t.adroja@rl.ac.uk

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Issue

Vol. 76, Iss. 17 — 1 November 2007

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