| Summary: | Superconductors may be categorized into many classes based on their critical temperature, Tc, crystal structure, and the nature of their superconductivity. The magnetic fields and current densities must be kept below the critical values Bc, and Jc respectively to remain in a superconducting state. One of the classifications is based on how the superconducting materials behaved when exposed to weak, external magnetic fields Ba. According to the Meissner Effect, as weak magnetic fields are exposed to a superconducting material, no magnetic field will penetrate the material, Bin except for a small region surrounding it, Bout creating perfect diamagnetism. However, the superconductivity may break up when Ba increases which classify the materials into Type I and Type II superconductors. In Type I superconductors, there is only one critical magnetic field Bc which separates the superconducting and non-superconducting states of the materials. The BCS theory has successfully explained the superconductivity in low-temperature superconductors based on the formation of the electron Cooper pairs, enabling them to occupy the same ground energy level. In Type II superconductors, the formation of two critical magnetic fields, Bc1 and Bc2 creates the Vortex or Mixed State in the between. Below Bc1, the materials behaved as a superconductor and lost their superconductivity above Bc2. The differences between Type I and Type II superconductors may well be explained based on their changes between resistance and critical temperature, magnetization, and Ginzburg-Landau parameters, κ. © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2022.
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