Study Of Crystal Growth And Magnetic Ion Doping Effect Of Transition Metal Oxides Heavy Fermion System CaCu₃Ru₄O₁₂

Heavy fermions system refers to the compounds whose itinerant electrons exhibit large effective mass. This unique system attracts attentions from scientists working in condensed matter physics due to their various ground state and intriguing properties. Conventionally, heavy fermions are found in f-electron compounds, however, recent research shows that heavy fermions can also be found in d-electron compounds, and CaCu3Ru4O12 is a member of d-electron heavy fermions system. The main work of this dissertation is about single crystal growth and doping effect on CaCu3Ru4O12. The dissertation is formed by the following aspects:1. Single crystals CaCu3Ru4O12 have been synthesized by flux method. The size of single crystal CaCu3Ru4O12 reached 1×1×1 mm3 for the first time. X-Ray diffractions identified the surface to be (100) surface. The rocking curve of (400) Brag peak of the CaCu3Ra4O12 single crystal showed that the full width at half-maximum was approximately 0.02 degree, implying the high quality of the single crystal. In addition, the result of magnetic susceptibility and electric resistivity along [100] direction and specific heat showed that the single crystal CaCu3Ru4O12 had the following properties:(1) metallic in the temperature range of 2 K to 300 K;(2) Fermi liquid behavior between 2 K and 30 K; (3) electron specific heat coffeicient is 90 mJ/(f.u. mol K2), which further confirms that CaCu3Ru4O12 is a heavy fermion system.2. Study of CaCu3Ru4-xMxO12 (M=Fe and Co) reavled that B site magnetic ion doping would increase the electron specific heat coffeicient ? as well as effective mass. For x=0.2 (M=Fe) polycrystal, single crystal and x=0.2 (M=Co) polycrystal, the value of ? are 270 mJ/(f.u. mol K2),128 mJ/(f.u. mol K2) and 183 mJ/(f.u. mol K2) respectively, all of which are larger than ? of CaCu3RuO12.Mass enhancement of all the doped samples may result from additional Kondo effect between localized electron from magnetic ion and itinerant Ru 4d electrons, which may increase the density of states at Fermi energy D(EF). In addition, an upturn is observed in the curve of CP/T-T2 of all doped samples. Applied fieds depress the upturn significantly. For Fe doped polycrystalline samples, a peak is appeared in the curve of ?C/T-T, which is located in 0.50 K,0.69 K,2.3 K for x=0.04, x=0.1, x=0.2 respectivley. Applied fields depress the peak and shift it to higher temperarute, which implies B site magnetic ion doping may induce magnetic order state. Results of ac magnetic susceptibility and dc magnetism relaxation of x=0.2 (M=Fe) polycrystal further confirm that its ground state is spin glass.3. Study of CaCu3-xNxRu4O12 (N=Zn and Ni) revealed the following features: Zn doping on A'site has little influence on effective mass and ground state of CaCu3Ru4O12. ? of Ni doped samples increases at first then decreases with x increasing. Amongy them, ? of x=0.15 is maximum,129 mJ/f.u. mol K2. Moreover, an upturn is observed in Cp/T-T2 curve of all the doped samples, which is depressed by applied fields. Non-monotonic dependence of y on x is because that Ni doping not only induce single ion Kondo effect, which will increase D(EF), but also cause dilution of Cu so as to decrease D(EF). Dilution of Cu may destroy Kondo lattice based on Kondo scenario so as to decrease D(Ef), and may reduce the Cu dxy bands'contribution to D(EF) as well. Ni doping is a parameter to modulate the competition, therefore, y of Ni doped samples shows non-monotonic variation with x.