Magnetic properties of layered superconductors

The magnetic properties of layered superconductor compounds are analyzed with the Josephson model of interlayer coupling. It is shown that, with the magnetic field oblique to the layers, a “three-dimensional” vortex structure appears in the system, where the local magnetic field intensity is modulated in the planes of layers as well as in the z-direction normal to them. When the modulation period in the z-direction is comparable with the period of the crystal lattice, then the energy of the system passes through a local minimum. This leads to a stabilization of the three-dimensional vortex structures at certain discrete values of angle θN. The Ginzburg-Landau differential-difference equation is derived again and certain significant terms are shown in it which those authors have neglected. An attempt is made to compare the predictions based on this study with the experimental results obtained by Morris and Coleman.

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