Itinerant and localized paramagnetism in Co doped CaCu₃Ru₄O₁₂

CaCu 3 Ru 4 O 12 is a Pauli paramagnetic metal oxide consisting of both 3 d and 4 d magnetic ions in a Cubic-perovskite crystal structure. This present work probes a change in magnetic ground state with the influence of Co. Polycrystalline CaCu 3 Ru 4- x Co x O 12 (0 ≤ x ≤ 0.1) powder samples have been prepared by conventional solid state reaction under ambient condition. X-ray photoelectron spectroscopy suggests the formation of Cu 3+ and Co 3+ ions. The absence of electron paramagnetic resonance (EPR) signal for x = 0.1 also confirms the presence of low spin Cu 3+ in doped system. Partial replacement of Ru 4+ by Co 3+ leads to a transition from itinerant Pauli to localized paramagnetism. Resistivity follows Fermi liquid behavior at low temperature.