Comparisons of electrical, magnetic and low temperature specific heat properties in group 13 and group 14 Ce 8Pd 24M compounds (M=B, Al, Ga, In and Si, Ge, Sn, Pb)

Abstract

The Ce 8Pd 24M compounds, with an ordered structure derived from CePd 3, have been synthesized for various group 13 and 14 p-block elements. The electrical resistivities of the group 13 compounds have features that can be attributed to strong Kondo interactions while the group 14 compounds show typical metallic behavior. The thermopowers, or Seebeck coefficients, for each compound were measured at both 297 and 78 K, and are much smaller (| S|<25 μV/K) than the relatively large values for CePd 3 ( S≈90 μV/K). All the compounds show Curie–Weiss behavior in the magnetic susceptibility confirming the formation of nearly trivalent moments and the loss of the intermediate valence state found in CePd 3. The low-temperature magnetic susceptibility also indicates antiferromagnetic ordering for all the compounds except M=B. The low-temperature specific heat was measured to investigate features of the antiferromagnetic ordering and potential heavy fermion behavior. While all the Ce 8Pd 24M compounds showed enhanced electronic specific heat ( C el) above the magnetic transitions, the group 13 compounds had larger values than the group 14 compounds. The group 13 compounds also showed anomalies in the magnetic ordering behavior. While these properties in the group 13 materials could be due to heavy fermion behavior, there are several other possible explanations for the high C el values and heavy fermion behavior cannot be definitively proved.