STUDY ON SCATTERING OF CONDUCTION ELECTRONS FOR SPIN-FLUCTUATION MEDIATED SUPERCONDUCTOR VIA dHvA EFFECT

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Scattering lifetime and effective mass of the conduction electrons for the spin-fluctuation mediated superconductor have been investigated by the de Haas-van Alphen (dHvA) effect. We selected typical compounds ZrZn_2 and CeIn_3 for the itinerant ferromagnet and magnetically ordering heavy Fermion system, respectively, both showing the unconventional superconductivity.Pressure study of dHvA effect on ZrZn_2 revealed"nested"ferromagnetic pressure-magnetic field phase diagram being similar to that of UGe_2. However, no significant changing of the scattering lifetime and the effective mass across the phase boundary was observed in ZrZn_2. Such a feature is different from that of UGe_2 in which drastic changing of the effective mass is observed. These results suggest that the conduction electron is more sensitive for the spin fluctuation through the felectron than the d-electron.vThe dHvA frequency and the effective mass of CeIn_3 change in behavior at distinct four pressures. These successive evolutions of the conduction electron properties are quite different from the sudden changes of them observed in sister compound CeRh_2Si_2. Although most of unconventional superconductors mediated by spin-fluctuation seem to possess a similar phase diagram, precise properties of conduction electrons are characteristic for each compound.