Low-Temperature Specific Heat of Ce_xLa_1−xCu₆

Abstract

Specific heat of a dense-Kondo system Ce_xLa_1−xCu₆(x=0.0, 0.1, 0.3, 0.5, 0.9 and 1.0) has been measured systematically down to 0.1 K in various magnetic fields up to 5 T in order to clarify the transition from dilute- to dense-Kondo behavior and the nature of the heavy-fermion ground state. In zero field, the magnetic specific heat per molar Ce, C_m, increases as the Ce concentration decreases. This tendency is attributed to the decrease of the Kondo temperature caused by the ‘chemical expansion’ effect. In a magnetic field applied along the c-axis, C_m⁄T is strongly suppressed. The observed behavior of C_m⁄T is interpreted by using a ‘resonance model’ with the Lorentzian density of states at the Fermi level, and for the dense system, CeCu₆ the experiments suggest the development of the ‘dense’ effect below 2 T.