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You searched for subject:(Oxygen vacancy ordering). Showing records 1 – 2 of 2 total matches.

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University of New South Wales

1. Chang, Fenfen. Search for novel multifunctional materials: a comprehensive neutron and synchrotron diffraction study on cobaltates and spinels.

Degree: Physics, 2017, University of New South Wales

Multiferroics exhibit tremendous potential in technological applications, of which the interplaybetween the ferro-/antiferromagnetic, ferroelectricity, and ferroelasticity can be manipulatedby external parameters such as electric or magnetic fields and even can be created byproper control of internal parameters, such as oxygen-content, cation doping, and internalpressure. Invaluable insight into the multiferroicity can be provided by investigating the roleof such parameters in the crystallographic and magnetic structures of transition metal oxides.In this thesis, a comprehensive studies of contribution of oxygen-deficiencies and cation dopingto the various phases are presented, which utilize the neutron and synchrotron powderdiffraction.The multivalent nature of cobalt ions in SrCoO3􀀀d causes an oxygen-content dependentphase diagram. It is vital to determine the precise crystallographic and magnetic structure ofoxygen-vacancy ordered SrCoO3􀀀d , which provides prerequisite to reveal the mechanism ofits multiferroicity in the corresponding thin film samples. Using the neutron and synchrotronpowder diffraction techniques, the correct space group and precise magnetic structures aredetermined for the different oxygen-vacancy ordered phases: the brownmillerite SrCoO2:5,the tetragonal SrCoO2:875, and the cubic SrCoO3.Ferroelectricity can be induced by the canted spin configuration, which exists widely inthe frustrated spin systems. With such an expectation, Zn-substituted CuFe2O4 was studiedand a comprehensive phase diagram was built for Cu1􀀀xZnxFe2O4. Spin canting couldlead to a spin spiral phase which could possibly induce a multiferroic state as observed inCuFeO2. The purpose of this project was to further investigate the spin canting in ZndopedCuFe2O4 and elucidate the possibility of multiferroicity in this system. Furthermore,pure ZnFe2O4 is already an interesting highly frustrated spin system. Magnetite is the oldestknown magnet. As the first known multiferroics, the ferroelectricity in Fe3O4 is drivenby the Verwey transition. However, the microscopic origin of the Verwey transition in Fe3O4is still in debate. In order to obtain a deeper insight into the mechanism of the charge ordering,Cu-doped Fe3O4 was investigated using the high-resolution neutron and synchrotrondiffraction. The main emphasis was the stability of the Verwey transition with charge carrierdoping. Advisors/Committee Members: Ulrich, Clemens, Physics, Faculty of Science, UNSW, Sushkov, Oleg, Physics, Faculty of Science, UNSW.

Subjects/Keywords: Oxygen vacancy ordering; Neutron diffraction; Synchrotron powder diffraction; Verwey transition; Charge ordering

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APA (6th Edition):

Chang, F. (2017). Search for novel multifunctional materials: a comprehensive neutron and synchrotron diffraction study on cobaltates and spinels. (Doctoral Dissertation). University of New South Wales. Retrieved from http://handle.unsw.edu.au/1959.4/57563 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:43656/SOURCE02?view=true

Chicago Manual of Style (16th Edition):

Chang, Fenfen. “Search for novel multifunctional materials: a comprehensive neutron and synchrotron diffraction study on cobaltates and spinels.” 2017. Doctoral Dissertation, University of New South Wales. Accessed January 24, 2021. http://handle.unsw.edu.au/1959.4/57563 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:43656/SOURCE02?view=true.

MLA Handbook (7th Edition):

Chang, Fenfen. “Search for novel multifunctional materials: a comprehensive neutron and synchrotron diffraction study on cobaltates and spinels.” 2017. Web. 24 Jan 2021.

Vancouver:

Chang F. Search for novel multifunctional materials: a comprehensive neutron and synchrotron diffraction study on cobaltates and spinels. [Internet] [Doctoral dissertation]. University of New South Wales; 2017. [cited 2021 Jan 24]. Available from: http://handle.unsw.edu.au/1959.4/57563 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:43656/SOURCE02?view=true.

Council of Science Editors:

Chang F. Search for novel multifunctional materials: a comprehensive neutron and synchrotron diffraction study on cobaltates and spinels. [Doctoral Dissertation]. University of New South Wales; 2017. Available from: http://handle.unsw.edu.au/1959.4/57563 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:43656/SOURCE02?view=true


University of Minnesota

2. Bose, Shameek. Complexity at cobaltite interfaces: the interplay between strain, stoichiometry, magnetism and transport.

Degree: PhD, Material Science and Engineering, 2014, University of Minnesota

Thin films and heterostructures of the perovskite cobaltites are of great interest, not only from the point of view of fundamental physics and materials science, but also for technological applications such as solid oxide fuel cells and gas membranes. Their properties are, however, severely deteriorated from the bulk, being dominated by the presence of interfacial "dead layers". Working with the prototypical SrTiO3 (001)/La1-xSrxCoO3 (LSCO) system, our group recently discovered that this degradation in the magnetism and electronic transport at the interface is caused by nanoscopic magneto-electronic phase separation. This was shown to occur primarily due to accumulation of oxygen vacancies near the interface, driven by the interplay between the strain state and the ordering of oxygen vacancies. In the present work we show how this understanding allows for engineering of the interfacial magnetic and electronic transport properties via manipulation of this oxygen vacancy superstructure. We first demonstrate a synthesis technique that utilizes a unique high pressure oxygen plasma to sputter LSCO thin films over a wide doping range 0.05  x  0.80. Then, using reciprocal space mapping and transmission electron microscopy, we demonstrate the ability to control, via the vacancy ordering, the critical strain relaxation thickness by changing the sign of the strain (from tensile on SrTiO3 to compressive on LaAlO3) and crystallographic orientation ((001) vs. (110)). We then provide cross sectional electron energy loss spectroscopy data to show that this strain and orientation control preserves both oxygen and hole carrier concentration at the LaAlO3(001)/LSCO and SrTiO3(110)/LSCO interfaces, strikingly different to the severely depleted SrTiO3(001)/LSCO interface. SQUID magnetometry, polarized neutron reflectometry (PNR) and magneto-transport confirm the concomitant mitigation of the interfacial degradation for LSCO films grown on LaAlO3(001) and SrTiO3(110), as compared to films grown on SrTiO3 (001). Finally, we use scanning tunneling microscopy to provide direct real space images of the magneto-electronic phase separation in ultrathin LSCO on SrTiO3(001). Our work thus demonstrates the ability to utilize oxygen vacancy ordering as a tunable control parameter to tailor interfacial electronic and magnetic properties, with profound implications for the myriad other systems that exhibit unique properties due to such ordering.

Subjects/Keywords: Cobaltite; Interface; Magnetism; Oxygen vacancy ordering; Strain; Thin film; Material science and engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Bose, S. (2014). Complexity at cobaltite interfaces: the interplay between strain, stoichiometry, magnetism and transport. (Doctoral Dissertation). University of Minnesota. Retrieved from http://hdl.handle.net/11299/170915

Chicago Manual of Style (16th Edition):

Bose, Shameek. “Complexity at cobaltite interfaces: the interplay between strain, stoichiometry, magnetism and transport.” 2014. Doctoral Dissertation, University of Minnesota. Accessed January 24, 2021. http://hdl.handle.net/11299/170915.

MLA Handbook (7th Edition):

Bose, Shameek. “Complexity at cobaltite interfaces: the interplay between strain, stoichiometry, magnetism and transport.” 2014. Web. 24 Jan 2021.

Vancouver:

Bose S. Complexity at cobaltite interfaces: the interplay between strain, stoichiometry, magnetism and transport. [Internet] [Doctoral dissertation]. University of Minnesota; 2014. [cited 2021 Jan 24]. Available from: http://hdl.handle.net/11299/170915.

Council of Science Editors:

Bose S. Complexity at cobaltite interfaces: the interplay between strain, stoichiometry, magnetism and transport. [Doctoral Dissertation]. University of Minnesota; 2014. Available from: http://hdl.handle.net/11299/170915

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