Magnetic properties of RPd5Al2 (R=Y, Ce, Pr, Nd, Sm, Gd)

Abstract

Abstract Polycrystalline samples of a new rare-earth series R Pd 5 Al 2 crystallizing in the tetragonal ZrNi 2 Al 5 -type structure have been prepared. Their physical properties by electrical resistivity ρ , magnetic susceptibility χ , magnetization M and specific heat C p measurements are reported. The ingots are composed of elongated grains preferentially aligned in the c direction; therefore, measurements were conducted parallel and perpendicular to the grains. Antiferromagnetic ordering appears in R =Ce, Nd, Gd, and Sm at low temperatures. CePd 5 Al 2 has two AFM transitions at 4.1 and 2.9 K and ρ ( T ) indicates a Kondo metal behavior with large anisotropy. In PrPd 5 Al 2 no magnetic transition was observed down to 0.4 K. The C p ( T ) shows a broad peak around 13 K due to the CEF effect, suggesting a non-magnetic singlet ground state. In NdPd 5 Al 2 , χ ( T ) shows anisotropy and the C p ( T ) shows a sharp peak at 1.2 K. The magnetic entropy at 3 K is very close to R ln2, indicating a Kramers doublet ground state. In SmPd 5 Al 2 , C p ( T ) shows a magnetic transition at 1.7 K. C p ( T ) for GdPd 5 Al 2 shows a peak at 6 K, followed by a broad anomaly around 3 K. Within this series, T N 's for CePd 5 Al 2 and NdPd 5 Al 2 clearly deviate from the relation predicted by de Gennes scaling, which is ascribed to the CEF effect.