Fluxointi

Fluxointi is a Finnish term that translates to "flux penetration" or "flux invasion" in English. It describes the phenomenon where a magnetic field penetrates into a superconductor. Superconductors typically exhibit a Meissner effect, expelling magnetic fields from their interior below a critical temperature and critical magnetic field strength. However, when the external magnetic field exceeds a certain threshold, the magnetic flux can begin to enter the superconductor.

There are two main types of superconductors that behave differently regarding flux penetration: Type I and Type II superconductors. In Type I superconductors, the magnetic field is completely expelled until the critical field is reached, at which point superconductivity is abruptly destroyed. In contrast, Type II superconductors allow magnetic flux to penetrate in discrete quantized units called magnetic flux vortices or fluxons. These vortices are essentially normal conducting cores surrounded by superconducting currents.

The penetration of flux in Type II superconductors occurs between a lower critical field (Hc1) and an upper critical field (Hc2). Below Hc1, the Meissner effect is complete. Between Hc1 and Hc2, the superconductor is in a mixed state or vortex state, where both superconducting regions and normal conducting flux vortices coexist. Above Hc2, superconductivity is completely lost. The study of flux penetration is crucial for understanding the behavior of superconductors in magnetic fields and for developing superconducting technologies, such as superconducting magnets and power transmission lines.