Magnetically measured irreversibility temperatures in superconducting oxides and alloys

Irreversibility temperatures T r (H) were magnetically measured for the aligned powders of superconducting oxides, La 1.85 Sr 0.15 CuO 4 , YBa 2 Cu 3 O 7 , Bi 2 Sr 2 CaCu 2 O 8 , and Bi 2 Sr 2 Ca 2 Cu 3 O 10 and for the metallic superconductors Nb, Nb-Ti, Nb 3 Sn and PbMo 6 S 8 . The results are briefly discussed in terms of the thermally activated flux creep and the lattice or the glass melting models for the irreversibility temperatures. Also, the measurement procedures for T r (H) using a SQUID magnetometer are described in detail, since the measuring methods and the criteria which are used for T r (H) are important in the determination and interpretation of the temperatures.