Ferromagnetism in orthorhombic RAgAl3 (R = Ce and Pr) compounds

We present a detailed study on magnetic, thermodynamic and transport properties of polycrystalline RAgAl3(R = Ce and Pr) compounds. Both compounds crystallize in orthorhombic structure, which is distorted from the tetragonal BaAl4 structure with the space group Cmcm. Heat capacity measurement indicates the bulk magnetic ordering of the compounds. CeAgAl3 and PrAgAl3 order ferromagnetically at TC=3.8 K and 5.8 K, respectively as it was confirmed from magnetic measurements. CeAgAl3 exhibits heavy fermion behaviour. The Schottky behaviour in heat capacity data was observed in both compounds. The crystalline electric field (CEF) analysis of the magnetic parts of heat capacity of CeAgAl3 and PrAgAl3 yielded to a CEF level scheme with three doublets and nine singlets and with an overall splitting of 51 K and 180 K, respectively. Fit yielded a magnetic doublet state for CeAgAl3, whereas for PrAgAl3 a pseudo-doublet ground-state with an energy difference of 15 K has been obtained. The resistivity measurements display a low temperature drop at the magnetic ordering temperature of the compounds. Negative magnetoresistance (MR) due to the ferromagnetic ordering has been observed for both Ce and Pr compounds.