Dramatic increase of paramagnetism before superconductivity quenches in Y1−XPrXBa2Cu3O7−δ

The samples of Y1−xPrxBa2Cu3Oy−δ were synthesized with 0 ⩽ X ⩽ 1.0 and characterized by DC magnetization measurement and X-ray diffraction. The structure of the samples was refined by Rietveld method. The paramagnetism in the samples increases with the increase of Pr dopant. We separate magnetization-temperature curves into two parts, paramagnetic and diamagnetic parts, trying to get more quantifiable analysis. After X = 0.4, the percent of paramagnetic part increases dramatically and finally destroys superconductivity. We attribute this dramatic increase of the paramagnetism to structural modulation, especially changes of the chemical bonds (such as: O2-Cu2-O2, O2-Cu2-O4 and O2-O4-O2). The results show that the origin of paramagnetism is strongly related to Cu2 in CuO plane. The relationship between the paramagnetism and superconductivity is discussed based on the experimental results.