Magnetic behaviour of (RPd3)8Al (R = Gd to Yb) and (CePd3)8Al0.5Zn0.5

Abstract

We have synthesized new compounds with the composition (RPd3)8Al (R = La,Gd, Tb, Dy, Ho, Er, Tm, Yb and Y) and (CePd3)8Zn0.5Al0.5. These compoundshave cubic symmetry and are iso-structural to (CePd3)8Al, reported earlier in theliterature. Compounds with R = Gd, Tb, Dy and Ho order magnetically above 1.6K and their transition temperatures are greater than those of the correspondingRPd3 analogues. (TbPd3)8Al shows an appreciable thermomagnetic irreversibilityin its magnetization measured in low fields below the Néel temperatureTN.The peak position in its ac susceptibility is frequency independent (1–999 Hz),which shows that the irreversibility is not driven by spin-glass-type freezing ofthe Tb moments. To a lesser extent, Dy and Ho compounds also exhibitirreversibility in their low-field magnetization below the Néel temperaturewhile it is absent in the Gd compound. Metamagnetic transitions are seenin the isothermal magnetizations of Tb, Dy and Ho compounds belowTNwhile such a feature is absent in the Gd compound. Resistivity mimima are seen forR = Gd, Tb, Dy and Ho and these arise most likely from the critical scattering aboveTN.The heat capacity data corroborate the long-range magnetic order in these fourcompounds and indicate a relatively low crystal electric field splitting. Thesubstitution of Al with Zn by as much as 50% in the parent dense Kondolattice antiferromagnet (CePd3)8Al expands the lattice marginally. Theresistivity of (CePd3)8Zn0.5Al0.5 shows Kondo behaviour and exhibits a peakaround 50 K. The corresponding feature in (CePd3)8Al occurs near 10 K.TNincreases marginally by 0.2 K due to the Zn substitution.