Heterogeneous magneto-superconducting systems /
We first present a new method to calculate the vortex and magnetization arrangement for a system of interacting superconductors and ferromagnets separated in space. The method is based on the static London-Maxwell equations and the corresponding energy. The possibility of superconducting (SC) vort...
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
2002.
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| Online Access: | http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=764785911&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | We first present a new method to calculate the vortex and magnetization arrangement for a system of interacting superconductors and ferromagnets separated in space. The method is based on the static London-Maxwell equations and the corresponding energy. The possibility of superconducting (SC) vortices is included in this system. Using this method we analyze screening currents in a SC film induced by magnetic textures in a thin magnetic film. We assume that the two films are parallel and positioned close to each other, but interact exclusively via magnetic fields. We also consider the possibility of vortices within this SC film, and their interactions with the magnetic texture. As an example of such a magnetic texture we consider a single magnetic dot with magnetization perpendicular to the film. We derive the condition for which spontaneous formation of one, two or more vortices and antivortices is energetically favorable. We prove that, for a circular magnetic dot with perpendicular magnetization, when the vortex emerges in the SC film, the normal component of the magnetic field near the SC film changes sign outside of the dot range. Secondly, a square array of magnetic dots grown on a SC film in the presence of the antivortices is studied. We show that the symmetry of the array is spontaneously violated. The positions of the vortices and the antivortices are calculated, depending on the magnetization and the size of the dots. Next, ferromagnet-superconductor bilayers (FSB) are considered. The homogeneous state of a FSB with magnetization perpendicular to the layer can be unstable with respect to the formation of vortices in the superconducting layer. The developing topological instability in the FSB leads to formation of domains in which the direction ofthe magnetization in the magnetic film and the direction of vorticity in the superconducting film both alternate. These domain structures are studied both in the continuum and the discrete regimes. |
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| Item Description: | Vita. "Major Subject: Physics". |
| Physical Description: | ix, 68 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilm Inc. |
| Bibliography: | Includes bibliographical references (leaves 52-56). |