Flux pinning
From Free net encyclopedia
Flux pinning is the phenomenon where a magnet's lines of force (called flux) become trapped, or "pinned", inside a superconducting material. This pinning binds the superconductor to the magnet at a fixed distance. Flux pinning is only possible when there are defects in the crystalline structure of the superconductor (usually resulting from grain boundaries or impurities).
Importance of flux pinning
Flux pinning is desirable in high-temperature ceramic superconductors in order to prevent "flux creep", which can create a pseudo-resistance and depress both critical current density and critical field.
Degradation of a high-temperature superconductor's properties due to flux creep is a limiting factor constraining the use of these superconductors. SQUID magnetometers suffer reduced precision in a certain range of applied field due to flux creep in the superconducting magnet used to bias the sample, and the maximum field strength of high-temperature superconducting magnets is drastically reduced by the depression in critical field.
References
- Future Science introduction to high-temperature superconductors.
- American Magnetics tutorial on magnetic field exclusion and flux pinning in superconductors.Template:Condensedmatter-stub