We study the interaction between superconductors and ferromagnets in two
systems: a ferromagnet-superconductor bilayer, and a thin superconducting film with
a periodic array of magnetic dots upon it, with spontaneous vortices appearing in the
systems. We show that the superconducting phase transition is of the first order in a
ferromagnet-superconductor bilayer and of the second order in the superconducting
film with a periodic array of magnetic dots upon it. The shift of the transition
temperature, (delta)Tc, due to the presence of a ferromagnetic layer may be positive or
negative in the ferromagnet-superconductor bilayer and is always negative in the
superconducting film with a periodic array of magnetic dots upon it. The dependence
of (delta)Tc on geometrical factors and the external magneticfield is found. The theory
is extended to multilayer structures. Next, we study the anisotropy dependence of
the critical current in a thin superconducting film with a periodic array of magnetic
dots with magnetization perpendicular to the film with spontaneous vortices and
antivortices. The phase diagrams for the appearance of spontaneous vortices and
antivortices are given for the square arrays of circular and square F dots respectively
when the direction of the magnetization is parallel to the superconducting film.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/3959 |
| Date | 16 August 2006 |
| Creators | Wei, Hongduo |
| Contributors | Pokrovsky, Valery |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 315847 bytes, electronic, application/pdf, born digital |
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