Effect of electron doping on physical properties of misfit-layered cobaltite Ca3-xYxCo4O9

• Main Authors: Jiun-Jie Pan, 潘俊傑
• Other Authors: D.C. Ling
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/60088976320753481838

碩士 === 淡江大學 === 物理學系碩士班 === 94 === Physical properties of misfit-layered cobaltite Ca3-xYxCo4O9 (CYCO) with polycrystalline samples have been extensively investigated. Electrical resistivity of the Y-substituted sample monotonically increases with increasing Y content, which could be attributed to the decrease of the hole concentration by substitution of trivalent Y3+ for divalent Ca2+. The resistivity exhibits a broad minimum around T = Tmin. At T > Tmin, follows T2 dependence up to T* ~ 170 K for x = 0 and 230 K for x = 0.2 samples, indicating that CYCO is a strongly correlated Fermi liquid in metal state. Whereas T < Tmin, exhibits insulating-like behavior, ranging from 62 K with x = 0 up to 120 K with x = 0.2. The dln(R)/d(1/T), related to the energy gap of SDW, reveals a plateaus and increases with increasing Y content. It suggests that Tmin scales with the onset temperature of SDW and SDW is enhanced by the Y doping. Furthermore, the dln(R)/d(1/T) gradually decreases below a temperature T**, increasing with increasing field for x , at which ferrimagnetism sets in. The variation of interlayer coupling between the [Ca2CoO3] and [CoO2] subsystems caused by substitution-induced chemical pressure as well as valence state change of cobalt has profound influence on the correlated evolution of SDW and ferrimagnetism.