Abstract
The magnetic properties of the skutterudite compound have been investigated by heat capacity and inelastic neutron scattering measurements. Heat capacity measurements reveal a broad peak centered at , whose magnitude is much larger than that expected from a Schottky anomaly due to a cubic crystal electric field. At , inelastic neutron scattering experiments clearly show the existence of a broad magnetic peak at . 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 , which is in very good agreement with the inelastic scattering data. Further, at , the inelastic response becomes purely quasielastic, which is in agreement with the theoretical calculations. Interestingly, the spin-gap energy in exhibits a universal scaling behavior with the Kondo temperature . 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.
1 More- Received 17 May 2007
DOI:https://doi.org/10.1103/PhysRevB.76.174438
©2007 American Physical Society