This dissertation mainly focuses on the investigation of the magnetic phase diagram of quasi two di- mensional triangular
lattice antiferromagnets (TLAFs) Ba₃MNb₂O9 (M = Co2+ (S = 1/2), Mn2+ (S = 5/2)), and their multiferroic properties. Both compounds show a
two-step magnetic phase transition at TN1 and TN2 upon cooling from paramagnetic to up-up-down(uud) phase due to the easy-axis anisotropy,
and 120 degree ordered phase at zero field. This feature is dissimilar to that of sister a compound Ba₃MNb₂O9 (Ni2+, (S = 1)), in which a
single magnetic phase transition occurs due to the easy-plane anisotropy at zero field. Moreover, at low temperature below TN1, successive
magnetic phase transitions were observed in both compounds. However, in case of Co compounds, the range of magnetic field where the uud
phase stabilizes becomes wider at lower temperature whereas becomes narrower in case of Mn compounds. This different behavior is
originated from the nature of the fluctuations that stabilize the uud phase, that is, quantum and/or classical fluctuations. We also found
that the spin magnitude and spin structure play a crucial role in stabilizing the multiferroic ground state. Multiferroicity appears in
all magnetically ordered phase in the small-spin-system Co compound but only in 120 degree ordered state in the large-spin-system Mn
compound. The systematic studies on these compounds provide a highly valuable playground in the investigate of the effect of spin varied
from 1/2 to 5/2 in frustrated magnets and multiferroics, attract many interests and in the field. / A Dissertation submitted to the Department of Physics in partial fulfillment of the requirements for
the degree of Doctor of Philosophy. / Spring Semester 2016. / March 31, 2016. / Frustrated systems, Magnetism, Magnetoelectricity, Multiferroicity, Triangular Lattice / Includes bibliographical references. / Eun Sang Choi, Professor Co-Directing Dissertation; Efstratios Manousakis, Professor Co-Directing
Dissertation; Naresh Dalal, University Representative; Irinel Chiorescu, Committee Member; Volker Crede, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_360394 |
| Contributors | Lee, Minseong (authoraut), Choi, Eun Sang (professor co-directing dissertation), Manousakis, Efstratios (professor co-directing dissertation), Dalal, Naresh S. (university representative), Chiorescu, Irinel (committee member), Crede, Volker (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Physics (degree granting department) |
| Publisher | Florida State University, Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource (151 pages), computer, application/pdf |
| Rights | This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). The copyright in theses and dissertations completed at Florida State University is held by the students who author them. |
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