PHYSICAL-PROPERTIES OF THE CE(RU1-XFEX)(2)GE-2 SERIES

CeRu2Ge2 is a ferromagnet with T-c=7.5 K and localized Ce magnetic mom ent of similar to 2 mu(B), aligned along the c direction of the tetrag onal ThCr2Si2 type of crystalline structure. CeFe2Ge2 is a nonmagnetic moderate heavy fermion system (gamma=210 mJ/mol K-2). I, the present work we have monitored the change of the physical properties of CeRu2G e2 with Fe substitution using x-ray diffraction, ac susceptibility, ma gnetization, resistivity, heat capacity, and Mossbauer spectroscopy. T he results obtained allowed us to verify the influence of the unit cel l volume change on the variation of the physical properties of this se ries. We discuss the evolution of the physical properties of the Ce(Ru 1-xFex)(2)Ge-2 series of compounds in terms of the competition between Kondo effect and Ruderman-Kittel-Kasuya-Yosida interactions in the Do niach model. A tentative phase diagram is proposed to represent the ph ysical picture of this series. The variation of the hybridization stre ngth between f and p/d orbitals due to the change of the unit cell vol ume was investigated. It provides an important contribution to the evo lution of the physical properties of the Ce(Ru1-xFex)(2)Ge-2 series of compounds.