DISTRIBUTION OF PINNING ENERGIES IN METAL-(M) SUBSTITUTED YBA2CU3-XMXO7-Y

Distributions of pinning energies were determined for orthorhombic and tetragonal YBa2Cu2.9Fe0.1O7-Y samples. Both have nearly the same oxygen content and T(c). Although the distribution of the orthorhombic sample is similar to that of none-doped one in a energy range below 40 meV, pinning centers with pinning energies from 20 meV to 40 meV are diminished in the tetragonal sample. The difference in the pinning features is related to the difference in the configuration of oxygen vacancies in Cu(I)-O planes.