Kondo systems $\mathrm{Ce}{\left({\mathrm{Pd}}_{1-x}{M}_x\right)}_2{\mathrm{Al}}_3$ ($M=\mathrm{Cu}$ or $\mathrm{Ag}$) have been previously shown to display antiferromagnetic (AFM) or ferromagnetic (FM) ordering alternatively then produce a complex phase diagram of AFM-FM-AFM type depending on the substitution amount $x$. This paper reports the results of specific heat $C\left(T\right)$ until high temperatures $\left(T⩽150\mathrm{K}\right)$ for the above systems. A Schottky peak is observed for all the samples in the magnetic contributions to specific heat, $C_{\mathrm{mag}}\left(T\right)$, while deviating from a typical one on substitution. Unusual Schottky peaks that spread over a very wide temperature range with considerably small values can be confirmed at least around $x=0.2–0.3$ where FM ordering just occurs. The unusual Schottky peaks are phenomenologically associated with randomness in the crystal electric field induced by the $\mathrm{Pd}\text{−}M$ replacements, and the randomness is discussed as a probable origin of the AFM-FM transition. In addition, a comparison between the present systems and the relevant AFM-FM transition system ${\mathrm{CePd}}_2{\left({\mathrm{Al}}_{1-x}{\mathrm{Ga}}_x\right)}_3$ suggests that the mechanism for the FM ordering is different in the two cases.

• Received 12 March 2004

DOI:https://doi.org/10.1103/PhysRevB.70.174429