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Caroline A. Ross. Ng, Bryan Massachusetts Institute of Technology. Dept. of Materials Science and Engineering. Massachusetts Institute of Technology. Department of Materials Science and Engineering 2009-04-29T17:35:25Z 2009-04-29T17:35:25Z 2008 2008 http://hdl.handle.net/1721.1/45395 317404502 Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2008. Includes bibliographical references. Patterned pseudo spin-valve rings show great promise for device applications due to their non-volatility and variety of stable magnetic states. However, the magnetic reversal of these elements under an applied field is complex due to the magnetostatic coupling between the two ferromagnetic layers. Elliptical rings are electrically probed using highly symmetric Wheatstone bridges in conjunction with traditional four-point electrical measurements and micromagnetic simulations. New insight into domain wall nucleation and propagation events are elucidated. The resulting behavior is found to yield large signals at very low fields, making these devices ideal for device applications in data storage and computer logic. 360° domain walls are found to be extremely stable until fields as high as 10000e, but are positionally uncontrollable in elliptical rings. Rhombic rings were investigated as a geometry that can nucleate, propagate and pin domain walls more easily. Measurements and simulations confirm that the same reversal mechanisms exist and domain walls are more systematically positioned. The control over 3600 domain walls is valuable since reversals can occur without nucleation by decoupling the wall into a reverse domain. As a result, rhombic rings are useful as devices that can perform device functions at extremely low fields. by Bryan Ng. M.Eng. 96 p. eng Massachusetts Institute of Technology M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. http://dspace.mit.edu/handle/1721.1/7582 Materials Science and Engineering. Understanding magnetic field reversal mechanisms in mesoscopic magnetic multilayer ring structures Thesis application/pdf Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="7d021c1d-d123-4243-b30c-95da60802dab"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Language>eng</Language> <Title>Understanding magnetic field reversal mechanisms in mesoscopic magnetic multilayer ring structures</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2008</PublicationDate> <Authors> <Author> <DisplayName>Ng, Bryan</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>http://dspace.mit.edu/handle/1721.1/7582</License> <Keyword>Materials Science and Engineering.</Keyword> <Abstract>Patterned pseudo spin-valve rings show great promise for device applications due to their non-volatility and variety of stable magnetic states. However, the magnetic reversal of these elements under an applied field is complex due to the magnetostatic coupling between the two ferromagnetic layers. Elliptical rings are electrically probed using highly symmetric Wheatstone bridges in conjunction with traditional four-point electrical measurements and micromagnetic simulations. New insight into domain wall nucleation and propagation events are elucidated. The resulting behavior is found to yield large signals at very low fields, making these devices ideal for device applications in data storage and computer logic. 360° domain walls are found to be extremely stable until fields as high as 10000e, but are positionally uncontrollable in elliptical rings. Rhombic rings were investigated as a geometry that can nucleate, propagate and pin domain walls more easily. Measurements and simulations confirm that the same reversal mechanisms exist and domain walls are more systematically positioned. The control over 3600 domain walls is valuable since reversals can occur without nucleation by decoupling the wall into a reverse domain. As a result, rhombic rings are useful as devices that can perform device functions at extremely low fields.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>