This dissertation describes the characterization of the magnetic and electrical
properties of a unique class of transition metal complexes known as single-molecule
magnets (SMMs). The experimental work of this dissertation is focused on the SMMs
[(C6H15N3)6Fe8O2(OH)12]Br7(H2O)Br •8H2O (Fe8Br8), K6[V15As6O42(H2O)] • 8H2O (V15), as
well as the analogous cluster compounds [NH(C2H5)3]4[V84.5+V44+As8O40(H2O)]•H2O (V12)
and [(C6H15N3)4Fe4O(OH)5]I7 • 2.5 H2O (Fe4). SMMs are transition metal cluster complexes
that exhibit single-molecule hysteresis and quantum tunneling of the magnetization
(QTM). Fe8Br8 is one of the best characterized SMMs with its ground state spin S = 10,
while V15 exhibits SMM behavior with a spin of S = ½. The foci of our investigations
were the single-spin model in Fe8Br8, the basic electrical properties of V15 and V12,
and the synthesis and characterization of the analogous cluster compound Fe4. Chapter 2
describes the characterization (magnetic parameters and energetic location) of the S = 9
excited state in Fe8Br8 by high field electron paramagnetic resonance, while Chapter 3
focuses on the measurement of the unpaired electron density distribution in Fe8Br8 as
determined by 81Br solid state NMR. Both of these chapters bring into question the
validity of the currently accepted single-spin model for Fe8Br8. Chapter 4 details the
dielectric relaxation properties of V15 as determined by an ac impedance method. The
semiconductive behavior of both V15 and V12 is described in Chapter 5, along with its
comparison to optical absorption measurements, while the synthesis and magnetic
characterization of the new cluster compound Fe4 is described in Chapter 6. The summary
and main conclusions are presented in Chapter 7. The results presented herein should
make a significant contribution to the fundamental understanding of the mechanism of
quantum tunneling in Fe8Br8 and the basic electrical properties of SMMs for their
potential use in future applications. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial
fulfillment of the requirements for the degree of Doctor of Philosophy. / Degree Awarded: Fall Semester, 2004. / Date of Defense: July 12, 2004. / Electrical Transport, Magnetic Resonance, Single Molecule Magnets, Excited States / Includes bibliographical references. / Naresh Dalal, Professor Directing Dissertation; Stephan von Molnár, Outside Committee Member; Kenneth Goldsby, Committee Member; Oliver Steinbock, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_168616 |
| Contributors | Zipse, David (authoraut), Dalal, Naresh (professor directing dissertation), Molnár, Stephan von (outside committee member), Goldsby, Kenneth (committee member), Steinbock, Oliver (committee member), Department of Chemistry and Biochemistry (degree granting department), Florida State University (degree granting institution) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource, computer, application/pdf |
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