RESISTIVE BEHAVIOR AND INTERMEDIATE VALENCE EFFECTS IN LA1-XCEXPD3 AND CEPD3-XRHX

The electrical resistivity of CePd3, La1-xCe xPd3, CeRhxPd3-x and Ce Pd 3+x systems has been measured from helium temperature to 300 K. The resistivity of pure CePd3 rises from 125 μ Ω cm to 150 μ Ω cm as one cools from 300 K to 100 K. Below 100 K the resisitivity drops dramatically to 10 μ Ω cm at low temperatures. The same qualitative behavior, though less pronounced, is observed in other systems such as CeSn 3 which like CePd3 are believed to be of intermediate valence. For x<0.3 the system La1-xCexPd3 is believed to be trivalent. We observe Kondo-like behavior in this regime. For x near unity we observe that extremely small amounts of La eliminate the rapid fall in resistivity observed below 100 K for pure CePd3. These results suggest that this fall off is due to some type of cooperative Ce ion hehavior. The CeRhxPd3-x system allows one to monitor the effect on resistivity of varying the Ce valence from 3.45 in CePd3 to 4 in CeRh.64Pd2.36. We find that the magnitude of the resistivity rise (upon cooling from 300 K to low temperature) decreases as the Ce valence increases towards four.