Reluctance of the YBa2Cu3Ox oxygen-deficient ceramics

Influence of an external magnetic field on the reluctance of the YBa 2 Cu 3 O x ceramics is investigated. A significant reluctance of the oxygen-deficient ceramics (with critical temperature Tc < 77 K) is established for a sample in the normal state at T < 160 K. It is demonstrated that after ceramics annealing that restores the oxygen content to a nearly optimum value, the magnetic field has essentially no effect on the sample reluctance at temperatures exceeding Tc. To explain the revealed mechanisms, a model involving ferromagnetic clusters effectively decreasing the free carrier density is used.