TEMPERATURE-DEPENDENCE OF THE MAGNETIC-FIELD PENETRATION DEPTH VERSUSOXYGEN ORDERING IN SUBMICRON YBCO PARTICLES

The influence of oxygen ordering on the temperature dependence of the magnetic field penetration depth A is investigated in submicron YBa2Cu 3O6+x particles obtained by low-temperature (T-s = 800 - 850 degrees C ) synthesis from a sol-gel precursor. Additional O-O bonds created at low temperature synthesis hinder the oxygen ordering in Cu(1)O plane d espite of its high content (x > 0.82). Oxygen exchange as well as addi tional annealing stimulate tetra-ortho transition and oxygen ordering. A wide linear range is observed in lambda(ab)(-2)(T) for samples with highly disordered oxygen. This is attributed to strong phase fluctuat ions caused by local strains. A gauge-glass model with random distribu tion of order parameter phases describes the behavior of lambda(ab)(-2 )(T), revealed at initial stage of the hindered tetra-ortho transition . Transformation of the linear lambda(ab)(-2)(T) fuction to a quadrati c one with oxygen ordering is related to decreasing of local deformati ons and to transformation from a glass state to the usual superconduct ing orthophase. Two essentially different ways of oxygen ordering, reo xidation and additional annealing, result in the same final state with a similar power law of lambda(ab)(-2)(T).