Spherical barium ferrite nanoparticles and hexaferrite single crystals for information data storage and RF devices

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dc.contributor Lane, Alan M.
dc.contributor Choi, Byoung-Chul
dc.contributor Li, Dawen
dc.contributor Kim, Seongsin
dc.contributor.advisor Hong, Yang-Ki
dc.contributor.author Jalli, Jeevan Prasad
dc.date.accessioned 2017-03-01T17:21:51Z
dc.date.available 2017-03-01T17:21:51Z
dc.date.issued 2014
dc.identifier.other u0015_0000001_0001779
dc.identifier.other Jalli_alatus_0004D_12118
dc.identifier.uri https://ir.ua.edu/handle/123456789/2225
dc.description Electronic Thesis or Dissertation
dc.description.abstract Since their discovery in the early 1950's hexagonal ferrites or hexaferrites have been studied for a long time because of their technological applications, such as microwave devices and high density magnetic recording media. In this dissertation efforts have been made to address these two applications by developing nanosized spherical barium ferrite particles for advanced magnetic recording media, and hexaferrite single crystals for low loss RF devices. Accordingly, this dissertation consists of two parts; part one spherical barium ferrite nanoparticles for information data storage media, and part two hexaferrite single crystals for RF devices. Part I. Spherical Barium Ferrite Nanoparticles Hexagonal barium ferrite (H-BaFe) nanoparticles are good candidates for particulate recording media due to their high uniaxial magnetocrystalline anisotropy, excellent chemical stability, and narrow switching field distribution. One major disadvantage of using H-BaFe particles for particulate recording media is their poor dispersion and a high degree of stacking that deteriorate the recording capability by creating large media noise and surface roughness. One way to solve and improve the recording performance of H-BaFe media is employing substantially nanosized spherical barium ferrite (S­BaFe) particles. Spherical shaped particles have low aspect ratio and only form a point-to-point contact, unlike the H-BaFe particles. Therefore, using S-BaFe particles not only decrease the degree of magnetic interaction between the particles but also can substantially increases the recording performance by improving the dispersion and SNR of the particles in the magnetic media. In this dissertation, two different approaches were employed successfully to synthesize S-BaFe nanoparticles in the range of 20-45 nm. Part II. Hexaferrite Single Crystals As wireless communication systems are flourishing, and the operating frequencies are increasing, there is a great demand for RF devices such as circulators and isolators. Traditional RF devices using spinel or garnets are disadvantageous in the millimeter range frequencies, since they require a strong external bias field provided by external permanent magnets. A promising approach to circumvent this problem is to use the high crystalline anisotropy field in the hexaferrites. Single crystals of M and Y-type hexaferrites show promising results with their low microwave losses and excellent magnetic and physical properties. In this dissertation efforts to grow, high-quality bulk M and Y-type single crystals with the aim to study and improve their magnetic and microwave properties with respect to different cation dopant elements is reported. Also, a liquid phase epitaxial technique was developed to grow thick barium ferrite films onto semiconductor substrates. Finally, magnetic domain patterns on bulk M-type single crystals was studied by using a magnetic force microscopy technique.
dc.format.extent 188 p.
dc.format.medium electronic
dc.format.mimetype application/pdf
dc.language English
dc.language.iso en_US
dc.publisher University of Alabama Libraries
dc.relation.ispartof The University of Alabama Electronic Theses and Dissertations
dc.relation.ispartof The University of Alabama Libraries Digital Collections
dc.relation.hasversion born digital
dc.rights All rights reserved by the author unless otherwise indicated.
dc.subject.other Engineering
dc.subject.other Materials Science
dc.subject.other Nanotechnology
dc.title Spherical barium ferrite nanoparticles and hexaferrite single crystals for information data storage and RF devices
dc.type thesis
dc.type text
etdms.degree.department University of Alabama. Dept. of Electrical and Computer Engineering
etdms.degree.discipline Electrical and Computer Engineering
etdms.degree.grantor The University of Alabama
etdms.degree.level doctoral
etdms.degree.name Ph.D.


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