Diamagnetic Shielding by a Superconductor

Hence 4 M = -Hj, and the volume susceptibility for a long thin superconducting cylinder with its axis oriented parallel to the applied field is given by  

The shielding fraction is a comparison between the measured volume susceptibility and -1/4, and it is given simply by -4 xv 

For a field applied parallel to the broad face of a thin rectangular plate of thickness d, the penetration depth reduces the shielding susceptibility by (25)  

Another complication is the demagnetization correction due to the geometry of the specimen. Demagnetization (or the equivalent depolarization problem for dielectric bodies in an electric field) can only be solved analytically for an ellipsoid of revolution (27X28). When He is applied parallel to one of the three axes of revolution, the magnetization is parallel to He, but the internal field H is given by (29)  

Since D is between 0 and 1 in all cases and xv 0, demagnetization produces an enhanced experimental susceptibility compared to the true volume susceptibility. 

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