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Theoretical and experimental studies...

Liu, Xiaofeng.

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Theoretical and experimental studies of layered magnetic systems.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Theoretical and experimental studies of layered magnetic systems./
作者:	Liu, Xiaofeng.
面頁冊數:	150 p.
附註:	Source: Dissertation Abstracts International, Volume: 65-12, Section: B, page: 6444.
Contained By:	Dissertation Abstracts International65-12B.
標題:	Physics, Condensed Matter. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3157395
ISBN:	9780496901449

Theoretical and experimental studies of layered magnetic systems.
Liu, Xiaofeng.

Theoretical and experimental studies of layered magnetic systems. - 150 p.

Source: Dissertation Abstracts International, Volume: 65-12, Section: B, page: 6444.

Thesis (Ph.D.)--Boston University, 2005.

This item must not be sold to any third party vendors.

This thesis presents the initial phase of experimental and theoretical studies of a new class of artificially grown antiferromagnetic (AF) materials, fabricated from composites of ultra-thin films (UTF's) that consist of alternating single- or multi-layered structures of cobalt and nickel oxides (CoO) n/(NiO)n. In my experimental work, I developed the methodology needed to grow highly-ordered NiO UTF's, as well as CoO/NiO UTF's on clean CoO (001) surfaces. I designed and developed a novel corona-discharge nozzle source capable of producing collimated beams of molecular oxygen, or of a mixture of atomic, molecular, and met,astable species of oxygen, well as Knudsen cells to produce collimated metal vapor beams. I carried out detailed studies of the effect of different growth parameters, such as substrate temperature and deposition flux rates. The growth was calibrated by Auger spectroscopy and monitored by He scattering, and the degree of ordering of the film was determined by diffraction profiles of elastically-scattered He beams. The success achieved in this work will open the way for future growth of more complex composites.

ISBN: 9780496901449Subjects--Topical Terms:

1018743
Physics, Condensed Matter.

Theoretical and experimental studies of layered magnetic systems.
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100 1 $a Liu, Xiaofeng. $3 3171530
245 1 0 $a Theoretical and experimental studies of layered magnetic systems.
300 $a 150 p.
500 $a Source: Dissertation Abstracts International, Volume: 65-12, Section: B, page: 6444.
500 $a Major Professor: Michael El-Batanouny.
502 $a Thesis (Ph.D.)--Boston University, 2005.
506 $a This item must not be sold to any third party vendors.
506 $a This item must not be added to any third party search indexes.
520 $a This thesis presents the initial phase of experimental and theoretical studies of a new class of artificially grown antiferromagnetic (AF) materials, fabricated from composites of ultra-thin films (UTF's) that consist of alternating single- or multi-layered structures of cobalt and nickel oxides (CoO) n/(NiO)n. In my experimental work, I developed the methodology needed to grow highly-ordered NiO UTF's, as well as CoO/NiO UTF's on clean CoO (001) surfaces. I designed and developed a novel corona-discharge nozzle source capable of producing collimated beams of molecular oxygen, or of a mixture of atomic, molecular, and met,astable species of oxygen, well as Knudsen cells to produce collimated metal vapor beams. I carried out detailed studies of the effect of different growth parameters, such as substrate temperature and deposition flux rates. The growth was calibrated by Auger spectroscopy and monitored by He scattering, and the degree of ordering of the film was determined by diffraction profiles of elastically-scattered He beams. The success achieved in this work will open the way for future growth of more complex composites.
520 $a I also carried out theoretical studies of the spin exchange mechanism in the (CoO)2/(NiO)2 superlattice, based on the Zaanen-Sawatzky formalism, and showed that in addition to the AF superexchange interaction, a ferromagnetic Co/Ni ex change component is present because of the extra d-electron on the Ni ion. I used Monte Carlo simulations to investigate the critical behavior as well as the competition between superexchange and double-exchange in the (CoO)2/(NiO)2 lattice system, where Coo is an Ising-like and NiO is a Heisenberg-like spin system. The correlation-length critical exponent v is found to be close to that of Ising. The competition between the two exchange mechanisms leads to two phase transitions in the system, and a slope discontinuity in the magnetization versus temperature curve occurs at the lower transition temperature. New phase diagrams, different from de Gennes's, were obtained, using Gelfert-Nolting's theory for a three-dimensional anisotropic Heisenberg system. A spin-canted state is possible only when there is a dominant direction for the competition of superexchange and double-exchange, as in the case of Pr1-xCa xMnO3, where the dominant direction is the result of charge ordering.
590 $a School code: 0017.
650 4 $a Physics, Condensed Matter. $3 1018743
650 4 $a Physics, Electricity and Magnetism. $3 1019535
690 $a 0611
690 $a 0607
710 2 $a Boston University. $3 1017454
773 0 $t Dissertation Abstracts International $g 65-12B.
790 $a 0017
791 $a Ph.D.
792 $a 2005
793 $a English
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