Fine structures of the oxygen K-edge in La2-xSrxCuO4-y (x=0, 0.15, 0.3 and 0.4), La1.85Ca0.15CuO4-y and La1.85Ba0.15CuO4-y were investigated by electron energy loss spectroscopy. The height of a peak at around 528 eV well corresponds to the hole content of the samples. In La2-xSrxCuO4-y, the peak height increases monotonically with the increase of Sr content (0≤ × ≤0.4), although Tc has a maximum at x = 0.15. The peak in La1.85Ca0.15CuO4-y is smaller than those of La1.85Sr0.15CuO4-y and La1.85Ba0.15CuO4-y. It is considered that the smaller peak corresponds to the smaller hole content and attributes to the lower Tc in La1.85Ca0.15CuO4-y than those of the other two superconductors.
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