2001-1

1) Vortex Phase Diagram of YBa₂(Cu_1-xZn_x)₃O_y Single Crystals

The vortex phase diagram of YBa₂(Cu_1-xZn_x)₃O_y single crystals with Zn concentration 0 ≦ x ≦0.064 have been investigated in magnetic fields up to 18 T. The first-order vortex lattice melting transition (T_m) and the field-driven disordering transition (H*) are extremely suppressed by small amount of Zn impurities. As for Zn-doped YBCO with x ≧ 0.001, the resistivity shows a broad superconducting transition due to the second-order vortex glass-to-liquid transition (T_g), while H* survives up to 0.003. These results suggest that disorders induced by Zn impurities strongly suppress the ordered vortex state such as the Bragg glass state in comparison with the oxygen deficiency.

IMR, Tohoku University: Takanori Sato, Terukazu Nishizaki, Kenji Shibata, Makoto Maki, Norio Kobayashi.
Reference : N. Kobayashi, T. Sato, T. Nishizaki, K.Shibata, M. Maki, T. Sasaki
"Vortex Phase diagram in Zn-doped YBa₂Cu₃O_y Crystals",
to be published in Proc. MOS2002 (J. Low Temp. Phys.)