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

Abstract: Polycrystalline samples of a new rare-earth series RPd5Al2 crystallizing in the tetragonal ZrNi2Al5-type structure have been prepared. Their physical properties by electrical resistivity ρ, magnetic susceptibility χ, magnetization M and specific heat Cp 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. CePd5Al2 has two AFM transitions at 4.1 and 2.9K and ρ(T) indicates a Kondo metal behavior with large anisotropy. In PrPd5Al2 no magnetic transition was observed down to 0.4K. The Cp (T) shows a broad peak around 13K due to the CEF effect, suggesting a non-magnetic singlet ground state. In NdPd5Al2, χ(T) shows anisotropy and the Cp (T) shows a sharp peak at 1.2K. The magnetic entropy at 3K is very close to Rln2, indicating a Kramers doublet ground state. In SmPd5Al2, Cp (T) shows a magnetic transition at 1.7K. Cp (T) for GdPd5Al2 shows a peak at 6K, followed by a broad anomaly around 3K. Within this series, T N''s for CePd5Al2 and NdPd5Al2 clearly deviate from the relation predicted by de Gennes scaling, which is ascribed to the CEF effect. [Copyright &y& Elsevier]