Critical current density determination of superconducting material

Knowledge of the law critical current density versus magnetic field, J_C(B), of a superconducting material is very important to users. In this article are presented two methods of characterization to obtain experimentally the law J_C (B). These two methods are commonly used for applications in electrical engineering. The electrical method is based on measuring the voltage and current of a superconducting sample. It has the advantage of simplicity in implementation, but the main drawback as the presence of the self magnetic field. This prevents the determination of the parameters of JC(B) for weak magnetic fields. The magnetic method using the cycle of magnetization has the advantage of making measurements without contact with the sample but has two drawbacks: it is based on a theoretical model in which JC is constant and the assumption of infinite length sample.