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Author:
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Category :
Languages : en
Pages : 8
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Book Description
This final report presents a review of the work accomplished on this contract. A review of the physics of hexagonal ferrite materials and the effective linewidth concept and the detailed overall research plan are contained in the original proposal document. The focus of the program was on the effective linewidth in millimeter wave materials, including planar hexagonal ferrite Y- type materials, uniaxial M-type materials, and thin ferromagnetic transition metal and alloy films. The key idea in the original proposal was that the ferromagnetic resonance linewidth in hexagonal ferrites is dominated by inhomogeneous and two-magnon scattering losses and that off-resonance measurements of the effective linewidth would (1) show that the FMR losses do not represent the intrinsic losses and (2) that the intrinsic losses are significantly lower. This basic idea was verified. Results were obtained on the off-resonance far-field effective linewidth in planar Zn-Y hexagonal ferrite single crystal platelets, single crystal spheres of Ba- and Sr-hexaferrite materials, and permalloy thin films. Three papers on these results have been published.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 8
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Book Description
This final report presents a review of the work accomplished on this contract. A review of the physics of hexagonal ferrite materials and the effective linewidth concept and the detailed overall research plan are contained in the original proposal document. The focus of the program was on the effective linewidth in millimeter wave materials, including planar hexagonal ferrite Y- type materials, uniaxial M-type materials, and thin ferromagnetic transition metal and alloy films. The key idea in the original proposal was that the ferromagnetic resonance linewidth in hexagonal ferrites is dominated by inhomogeneous and two-magnon scattering losses and that off-resonance measurements of the effective linewidth would (1) show that the FMR losses do not represent the intrinsic losses and (2) that the intrinsic losses are significantly lower. This basic idea was verified. Results were obtained on the off-resonance far-field effective linewidth in planar Zn-Y hexagonal ferrite single crystal platelets, single crystal spheres of Ba- and Sr-hexaferrite materials, and permalloy thin films. Three papers on these results have been published.
Author: Carl E. Patton
Publisher:
ISBN:
Category :
Languages : en
Pages : 13
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Book Description
This short term post LRCP contract was designed to explore the application of the off-resonance effective linewidth technique to hexagonal ferrite materials at x-band frequencies. This objective has been accomplished. It has been demonstrated that the technique works quite well for both uniaxial and planar ferrite materials. The key result for millimeter wave applications is that a significant part of the microwave losses in these materials appears to be related to inhomogeneities. The effective losses which would determine insertion loss parameters for off-resonance device applications would appear to be much lower than one would infer from a direct ferromagnetic resonance linewidth determination. It was also possible to use the technique to measure the off-resonance loss properties in uniaxial materials at x-band, even though the large anisotropy fields precluded the observation of the FMR peak. The application of the technique to planar samples has also led to a new approach to the analysis of fundamental microwave relaxation processes in ferrite materials. Keyword: Microwave damping.
Author: ARTHUR. TAUBER
Publisher:
ISBN:
Category :
Languages : en
Pages : 1
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The ever increasing traffic of the communications medium combined with an urgent need for secure tran mission of messages has directed attention to broadcasting at higher frequencies. The lower range of the microwave spectrum has been intensively exploited during the last twenty years. Attention is now focused at the upper microwave and millimeter wave spectrum, 10 to 70 kilomegocycles/sec. Before devices and systems can be designed components must be found that can operate at these higher frequencies. The synthesis of a series of single crystal hexagonal ferrites potentially useful in several different devices at microwave and millimeter wave frequencies is described. Some of the unique intrinsic properties which make these crystals applicable at these frequencies were measured and are reported. Several devices were constructed and operated with these crystals. The experimental results and potentialities of such devices are described. (Author).
Author: A. J. Baden Fuller
Publisher: IET
ISBN: 9780863410642
Category : Technology & Engineering
Languages : en
Pages : 296
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Book Description
Includes a full mathematical treatment of the interaction of an electromagnetic wave with a gyromagnetic ferrite material.
Author: C. Vittoria
Publisher:
ISBN:
Category :
Languages : en
Pages : 30
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Book Description
A survey was conducted in order to establish the usefulness of ferrites at millimeter wave frequencies. We expect hexagonal ferrites to be operational up to approximately 500 GHz for non-reciprocal device applications. The limiting factor of these type of ferrites at millimeter wave frequencies may possibly be that the dielectric propagation loss is too high. Beyond 500 GHz antiferromagnetic materials may have to be explored for possible uses. (Author).
Author: William E. Kramer
Publisher:
ISBN:
Category :
Languages : en
Pages : 119
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Book Description
During this program we surveyed a number of new substrate and solvent solution systems for epitaxial ferrite growth. the growth of single crystals of two new materials, cobalt gallate and Ta-substituted barium vanadate, was successfully demonstrated. Compositions lattice-matched to the ferrites were demonstrated, and ferrite films were grown on cobalt gallate. Interdiffusion of barium hexaferrite and barium vanadate prevented high-quality hexaferrite film growth on the latter substrate.
Author: Howard L. Glass
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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This program has consisted of an investigation of the liquid phase epitaxial growth of hexagonal ferrites. The objective has been to obtain high quality single crystal layers of hexagonal ferrite which would be suitable for use in millimeter-wave tunable filters. The specific objectives were to determine the conditions required for preparation of ferrites which would give ferromagnetic resonance at frequencies in the range of 50 to 70 GHz using magnetic bias fields available with present technology and having resonance linewidths no greater than 50 0e. The work consisted of the growth and preparation of gallate spinel substrate crystals, the liquid phase epitaxial growth of strontium hexaferrite layers on these substrates by means of a lead oxide - boron oxide flux, and the characterization of these materials. Techniques were devised for fairly reproducible growth of hexaferrites which had linewidths substantially less than 100 0e and which required fields of only about 7 K0e for resonance at 60 GHz. The best sample had a linewidth of 60 0e, a significant improvement over previous epitaxial hexaferrites. (Author).
Author: H. L. Glass
Publisher:
ISBN:
Category :
Languages : en
Pages : 25
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Book Description
The objective of this research was to develop single crystal hexagonal ferrite films of superior quality. These films would be useful in millimeter wave devices such as tunable filters. They also would be useful in studying basic magnetic phenomena in these materials; for example, their high magnetocrystalline anisotropy. A novel two-step liquid phase epitaxy (LPE) process was developed which resulted in improved quality of barium hexaferrite films deposited on gallate spinel substrates (indium substituted magnesium gallium oxide spinel). The two-step process entailed the growth of a thin epitaxial film of a spinel ferrite prior to deposition of the desired hexagonal ferrite. The hexagonal ferrite films obtained by this method were more uniform and more strongly bonded to the substrate than films grown without the intermediary spinel ferrite layer. The hexagonal ferrite films exhibited large, rounded hillocks that appeared to be associated with defects in the substrate crystals. Ferromagnetic resonance measurements were made at 60 GHz. External dc magnetic bias fields of about 9 KOe were required for resonance, as expected for barium hexaferrite. Resonance linewidths were about 50 to 60 oersted. Substantial reductions in linewidth should be achievable with further improvements in crystal quality. (Author).
Author:
Publisher:
ISBN:
Category : Military research
Languages : en
Pages : 284
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Author: Mailadil T. Sebastian
Publisher: John Wiley & Sons
ISBN: 1119208564
Category : Technology & Engineering
Languages : en
Pages : 997
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Book Description
Die jüngsten Fortschritte im Bereich der drahtlosen Telekommunikation und dem Internet der Dinge sorgen bei drahtlosen Systemen, beim Satellitenfernsehen und bei intelligenten Transportsystemen der 5. Generation für eine höhere Nachfrage nach dielektrischen Materialien und modernen Fertigungstechniken. Diese Materialien bieten ausgezeichnete elektrische, dielektrische und thermische Eigenschaften und verfügen über enormes Potenzial, vor allem bei der drahtlosen Kommunikation, bei flexibler Elektronik und gedruckter Elektronik. Microwave Materials and Applications erläutert die herkömmlichen Methoden zur Messung der dielektrischen Eigenschaften im Mikrowellenbereich, die verschiedenen Ansätze zur Lösung von Problemen der Materialchemie und von Kristallstrukturen, in den Bereichen Doping, Substitution und Aufbau von Verbundwerkstoffen. Besonderer Schwerpunkt liegt auf Verarbeitungstechniken, Einflüssen der Morphologie und der Anwendung von Materialien in der Mikrowellentechnik. Gleichzeitig werden viele der jüngsten Forschungserkenntnisse bei Mikrowellen-Dielektrika und -Anwendungen zusammengefasst. Die verschiedenen Kapitel untersuchen: Oxidkeramiken für dielektrische Resonatoren und Substrate, HTCC-, LTCC- und ULTCC-Bänder für Substrate, Polymer-Keramik-Verbundstoffe für Leiterplatten, Elastomer-Keramik-Verbundstoffe für flexible Elektronik, dielektrische Tinten, Materialien für die EMV-Abschirmung, Mikrowellen-Ferrite. Ein umfassender Anhang präsentiert die grundlegenden Eigenschaften von mehr als 4000 verlustarmen dielektrischen Keramiken, deren Zusammensetzung, kristalline Struktur und dielektrischen Eigenschaften für Mikrowellenanwendungen. Microwave Materials and Applications wirft einen Blick auf sämtliche Aspekte von Mikrowellenmaterialien und -anwendungen, ein nützliches Handbuch für Wissenschaftler, Unternehmen, Ingenieure und Studenten, die sich mit heutigen und neuen Anwendungen in den Bereichen drahtlose Kommunikation und Unterhaltungselektronik beschäftigen.
