Critical exponential behavior of metal oxide ceramic YBa2Cu3O9−<i>δ</i>

The process of degradation of superconductivity in low-resistivity ceramics YBa2Cu3O9−δ (R100∼10−3−1014Ω cm) is considered. It is found that over a wide range of currents I and temperature T, the transition to the normal state is accompanied by a critical exponential dependence of resistance on temperature for a given current (R(T) ∝ (T—Tc)tR) and of voltage U on current for a given temperature (U(I) ∝ (I—Ic)tU). The position of constant tR.U lines on the I–T plane of critical indices is determined. The critical behavior of diamagnetic moment M as a function of temperature for a given value of the modulating magnetic field is reported. It is predicted that the critical behavior of metal oxide ceramics can be described by using nontrivial operators whose scale has the same dimensionality as the space of the system.

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