Ph.D. (Doctor of Philosophy)
Department of Physics
Condensed matter; Physics
Multiferroic materials having unusual properties of simultaneous presence of ferroelectricity (FE) and magnetism, such that FE can be controlled by magnetic field and magnetization by electric field have attracted interest due to their promising applications in electrically controllable microwave elements, magnetic field sensors, and possibly in spintronics. In this dissertation, the single phase and single ion multiferroic properties of the ceramic oxide antiferromagnets (AFM) Sr[sub 1-x]Ba[sub x]Mn[sub 1-y]TiyO[sub 3] with perovskite structure are discussed. These compounds were designed and developed in our laboratory by understanding critical parameters controlling FE and magnetic properties, advancing the synthesis processes, studying the structural behavior and intricate transitions, and characterizing dielectric and magnetic properties over the complex phase diagram of the manganites system. Multiferroelectricity was achieved by forcing bonds between magnetic transition metals and oxygen under internal tension through the proper selection of the sizes and charges of the A-site and B-site cations as predicted based on the Goldschmidt tolerance factor. Synchrotron X-ray diffraction (XRD) and Neutron powder diffraction (NPD) experiments were used to study the structural, FE and magnetic properties. In the conventional FE titanates BaMn[sub 1-y]TiyO[sub 3], the solubility limit of manganese was extended to 1-y ~ 0.16, and the XRD data taken at Argonne's National Laboratory Advanced Photon Source showed increased temperatures of the coupled structural-ferroelectric transitions above 400 K. A complete solid solution range of manganese ion on the Ti-site was obtained in SrMn[sub 1-y]TiyO[sub 3] (0
Chapagain, Kamal, "Discovery and study of single-phase and single-ion manganese perovskite multiferroics" (2019). Graduate Research Theses & Dissertations. 2253.
Northern Illinois University
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Committee members: Brown, Dennis; Chmaissem, Omar; Ito, Yasuo; Sunderlin, Lee.||Advisor: Dabrowski, Bogdan.||Includes bibliographical references.