A specific-heat study of some RFe4Al8 compounds (R=Ce,Pr,Nd,Dy,Ho,Tm)

Specific-heat measurements have been performed on the tetragonal ThMn12-type RFe4Al8 compounds with R=Pr, Dy and Tm in the temperature range 1.5 to 200 K. The compound PrFe4Al8 gives rise to a λ-type anomaly at 11.3 K. In DyFe4Al8 we found anomalies at 8.6 K and at about 30 K, while in TmFe4Al8 there is an anomaly below 1.5 K. From the temperature dependence of the magnetic entropy in the presently studied compounds and from data obtained in earlier investigations, it is concluded that the overall crystal-field splitting in the RFe4Al8 compounds with R=Pr, Nd, Dy, Ho, Er and Tm is less than 200 K. (orig.)