Comparisons of electrical, magnetic and low temperature specific heat properties in group 13 and group 14 Ce8Pd24M compounds (M = B, Al, Ga, In and Si, Ge, Sn, Pb)

The Ce8Pd24M compounds, with an ordered structure derived from CePd3, have been synthesized for various group 13 and 14 p-block elements. The electric al resistivities of the group 13 compounds have features that can be attrib uted to strong Kondo interactions while the group 14 compounds show typical metallic behavior. The thermopowers, or Seebeck coefficients. for each com pound were measured at both 297 and 78 K, and are much smaller (\S\ < 25 mu V/K) than the relatively large values for CePd3 (S approximate to 90 mu V/ K). All the compounds show Curie-Weiss behavior in the magnetic susceptibil ity confirming the formation of nearly trivalent moments and the loss of th e intermediate valence state found in CePd3. The low-temperature magnetic s usceptibility also indicates antiferromagnetic ordering for all the compoun ds except M = B. The low-temperature specific heat was measured to investig ate features of the antiferromagnetic ordering and potential heavy fermion behavior. While all the Ce8Pd24M compounds showed enhanced electronic speci fic heat (C-el) above the magnetic transitions, the group 13 compounds had larger values than the group 14 compounds. The group 13 compounds also show ed anomalies in the magnetic ordering behavior, While these properties in t he group 13 materials could be due to heavy fermion behavior, there are sev eral other possible explanations for the high C-el values and heavy fermion behavior cannot be definitively proved. (C) 1999 Elsevier Science B.V. All rights reserved.