1-t ^{2 (1-α)}, a basic function to quantify magnetic measurements in high-Tc superconductors at low external magnetic fields

The magnetization of high-T_c superconductors as a function of temperature at low external magnteic fields is well described by curves that are based on the function 1-t ^{2 (1-α)}. We discuss three modela that generate this function; the two-fluid model, a field cooling remanent magnetization model and a zero field cooling magnetization model. The basic concepts of each model are different.