Pressure Effect on the Vortex Phase Diagram in Bi₂Sr₂CaCu₂O_8+y

抄録

Effects of hydrostatic pressure on the vortex phase diagram are studied in a highly anisotropic high temperature superconductor Bi₂Sr₂CaCu₂O_8+y. The local magnetization measured by using a micro-Hall-probe shows clear vortex lattice melting steps at high temperatures and the peak effect at low temperatures up to 1 GPa. We found that the pressure shifts these phase boundaries towards higher fields systematically. These changes are qualitatively unde0rstood by considering the reduction of the anisotropy γ of the system with pressure. The temperature dependence of pressure coefficient, however, suggests that there exists substantial contribution of the disorder to the phase boundaries in this system.