Effect of hydrostatic pressure on the resistance and critical temperature of YBa2Cu3O7-delta single crystals

The effect of hydrostatic pressure on the resistance and resistive transition to the superconducting state in YBa2Cu3O7-delta Single crystals with different oxygen contents is studied experimentally. It is found that, following the application (or removal) of pressure, the resistance relaxes to an equilibrium value that depends on pressure, the relaxation time at room temperature being about two days. It is shown that the value of the superconducting transition temperature depends on the pressure, but the width and shape of the transition depend mainly on the degree of resistance relaxation to the equilibrium value. It is concluded that the decrease in resistance under hydrostatic pressure is associated with the ordering of labile oxygen in the Cu-O plane. The possible mechanisms of variation of the superconducting transition temperature are discussed. (C) 1997 American Institute of Physics.