A specific-heat study of RMn4Al8 compounds (R=Y,La,Pr,Nd,Dy,Er)

Specific-heat measurements have been performed on the tetragonal ThMn12-type RMn4Al8 compounds with R=Y,La,Pr,Nd,Dy and Er in the temperature range 1.5 to 200 K. The compound PrMn4Al8 gives rise to a λ-type anomaly at 14 K. No anomalies indicative of magnetic ordering were found above 1.5 K in the specific-heat curves of the RMn4Al8 compounds with R=Y,La,Nd,Dy, and Er. From the temperature dependence of the magnetic entropy, it is concluded that the overall crystal-field splitting in the compounds with R=Pr,Nd,Dy, and Er is of the order of 200 K or even less. (orig.)