The Effect of In-Plane impurity on Superconductivity and Magnetism in Superconducting Weak Ferromagnet RuSr2RCu2O8 ( R=Gd, Eu )

• Main Authors: Shang-Lun Wu, 吳尚倫
• Other Authors: 林大欽
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/26211725416324553508

碩士 === 淡江大學 === 物理學系碩士班 === 98 === The polycrystalline bulk samples of RuSr2R(Cu1-xMx)2O8 (R = Gd, Eu，M = Ni, Zn) were synthesized by the solid-state reaction techniques, and have been extensively investigated for structure, magnetization, resistance, and MR ratio. In powder X-ray diffraction Rietveld refinement study, we found the doping of impurity make RuO6 octahedral distort and rotate about c-axis. The crystal structure may undergo a distorted-to-undistorted transition. The Tc suppression in Ni-doped samples displays a AG-like behavior, but it in Zn-doped samples doesn’t. With the increase of the impurity, the TM of doped samples of Ru-1212Gd and Ru-1212Eu become higher and lower respectively. In MR ratio measurement, MR ratio values are proportion to Hα with α=2 above 200 K, Below 200 K we find that α continuously decreases to a value of α=1 as the magnetic ordering temperature is approached. Furthermore, just below the magnetic ordering temperature, a positive magnetoresistance is observed for low applied magnetic fields. The positive magnetoresistance was interpreted as being due to orbital magnetoresistance or spin-flip. In higher applied magnetic field, we observe the negative magnetoresistance in doped Ru-1212Gd samples, but we still observe the positive magnetoresistance in doped Ru-1212Eu samples. It reveal that the magnetic crystal structures in doped Ru-1212Gd and doped Ru-1212Eu samples are obviously different below TM , It may account for that why the Tc suppression in Ni-doped and Zn-doped samples are distinct.