Specific heat of Ce1-xLaxRhIn5 in zero and applied magnetic field:: A rich phase diagram -: art. no. 134418

We report specific-heat results on a single crystal as well as some polycrystalline samples of Ce1-xLaxRhIn5. Determination of the magnitude of the specific heat gamma (equivalent toC/T as T-->0) as a function of concentration is made somewhat uncertain by the structure of the specific heat below 3 K. However, within our error bar, this gamma (less than or equal to100 mJ/Ce-mol K-2)-which differs by approximately a factor of 4 with previous estimates-seems consistent with the effective masses observed in recent de Haas-van Alphen measurements. We find, in addition, that (a) there exists a field-induced transition for xgreater than or equal to0.5 that increases in temperature with increasing applied magnetic field and (b) although single and polycrystalline materials give approximately the same specific heat for x=0.15 and 0.95, the second phase (removable via long-term annealing) in the polycrystalline material plays a role for x=0.5 and 0.8. Furthermore, the low-temperature specific heat shows an upturn in C/T at low temperature for xgreater than or equal to0.5 in both single-crystal and polycrystalline materials, which appears to be intrinsic. The field-induced anomaly, coupled with both the temperature and field dependence of the magnetization data and the temperature dependence of this low-temperature upturn in the zero field C/T (proportional to T-1+lambda) may be evidence for the Griffiths phase non-Fermi-liquid behavior due to the inherent disorder of doped samples.