Muon Spin Relaxation Studies of Heavy Fermion Systems

9510453 Luke Muon spin relaxation will be used to study the interplay between various interactions and phenomena in rare earth and actinide compounds. Many of these systems exhibit interesting magnetic behavior due to the combination of the Kondo effect, Rudman-Kittel-Kasuya Yosida interaction and the effect of crystalline fields. In materials where these interactions are present, such phenomena as heavy fermion superconductivity and quadrupole Kondo effect are observed. Superconductivity and antiferromagnatic ordering coexist in uraniumplatinum-three compound. This antiferromagnetism contributes to multiple superconducting phases. This research will help elucidate the microscopic nature of the different superconducting states. In another compound, cerium-copper2-silicon2, superconductivity and magnetism do not coexist but compete for the ground state. This work will investigate the competition between the two states. The competition between Kondo screening and exchange interactions will be studied in cerium-copper-two- tin-two. The relative importance of the crystalline electric fields, Kondo screening and exchange interactions will be determined in uranium doped yttrium-palladium- three. Theoretical models based on the anomalous low temperature linear specific heat in neodymium-cerium-copper- oxygen compound will be tested by way of the measurement of spin fluctuations in this compound. %%% Muon Spin Relaxation experiments will be conducted on a number of rare earth and actinide compounds which exhibit a rich interplay between various interactions and phenomena such as superconductivity and magnetic ordering. Five different studies will be conducted: (1) the coexistence between antiferromagnetic ordering and the microscopic nature of the resulting multiple superconducting phases, (2) the competition between magnetic ordering and superconductivity in a compound where they do not coexist, (3) the competition between Kondo screening and exchange interaction, (4) the relative importance between crystalline electric fields, Kondo screening and exchange interactions, and (5) fluctuation effects in materials which exhibit anomalous thermodynamic behavior. Each of the above study will be conducted on the appropriate compound. ***