The resistance of superconducting cylinders in a transverse magnetic field

Experiments on the penetration of a magnetic field (de Haas and Casimir-Jonker 1934) into superconductors have shown that, when a superconducting cylinder is placed in an increasing transverse field, penetration of the field first occurs when the applied field strength reaches a value 0·50Hk, where Hk is the critical field corresponding to the temperature of the experiment. Since, for this value of the applied field, the field strength, at the surface of the cylinder (von Laue 1932) where it is intersected by a diametral plane perpendicular to the direction of the field, will be precisely Hk, the above result is in accordance with expectation. On the other hand, it was found by de Haas, Voogd and Jonker (1934) that under the same conditions the cylinder first exhibited electrical resistance when the applied field strength reached the value 0·58Hk. Since this discrepancy probably results from the properties of the “intermediate state” (Peierls 1936; London 1936; Landau 1937) occurring when the magnetic field just begins to penetrate the superconductor, it seemed desirable to investigate the matter in more detail.