Abstract Metal eutectic fluxes are useful for exploratory synthesis of rare earth intermetallics. In this work, the use of rare earth/transition metal eutectics such as: Nd/Co,
Pr/Co, Ce/Co, Nd/Ni and Sm/Ni have yielded many structually and magnetically complex phases, which also help us to to gain better understanding of reactivity trends of various elements in
the flux. The intermetallic compounds R₂Co₂SiC (R = Pr, Nd) were prepared from the reaction of silicon and carbon in either Pr/Co or Nd/Co eutectic flux. These phases crystallize with a
new structure type in orthorhombic space group Immm, with unit cell parameters a = 3.978(4) Å, b = 6.094(5) Å, c = 8.903(8) Å (Z = 2; R₁ = 0.0302) for Nd₂Co₂SiC. Silicon, cobalt, and
carbon atoms are connected with each other to build up two-dimensional flat sheets which are separated by puckered layers of rare-earth cations. Magnetic susceptibility measurements
indicate that the rare earth cations in both analogs order ferromagnetically at low temperature (TC = 10 K for both). Single crystal neutron diffraction data for Nd₂Co₂SiC indicates this
ordering occurs in two steps. Crystals of two new germanide intermetallic compounds were grown from Nd/Co or Pr/Co eutectic flux. The crystal structure of Nd₈Co[subscript 4-x]Al[subscript x]Ge₂C₃ (Pbcm, a=8.00Å,
b=11.71Å,c=15.07Å; Z=4, R₁=0.0261) features germanium centered neodymium clusters Ge@Nd₉ capped with Co and C atoms which form infinite zigzag chains. Magnetic susceptibility measurements
indicate the Nd ions order at 50K. Magnetic anisotropy studies show the Nd[superscript 3+] magnetic moments tend to align ferrimagnetically along the c axis. The phase RE₆Co₅Ge[subscript 1+x]Al[subscript 3-x] (RE=Pr, Nd)
crystallizes with the Nd₆Co₅Ge[subscript 2.2] structure type in hexagonal space group P-6m2 (a = 9.203(2)Å, c = 4.202(1) Å, R1 = 0.0109 for Pr₆Co₅Ge[subscript 1.80]Al[subscript 2.20]; and a = 9.170(3) Å, c = 4.195(1) Å, R1 =
0.0129 for Nd₆Co₅Ge[subscript 1.74]Al[subscript 2.26]), featuring chains of face-sharing Ge@RE₉ clusters intersecting hexagonal cobalt nets linked by aluminum atoms. Magnetic susceptibility measurements indicate
that both phases exhibit ferromagnetic ordering of the cobalt layers with TC in the range of 130-140K, and the rare earth ions order at low temperature (30-40K). The magnetic measurements
on oriented crystals of Nd₆Co₅Ge[subscript 1.74]Al[subscript 2.26] show a strong preference of the Co moments to order along the c-axis. A cerium cobalt borocarbide compound, Ce₁₀Co[subscript 2.75]B[subscript 11.5]C₁₀(triclinic, P-1, a
= 8.5131(5)Å, b = 8.5144(5)Å, c = 13.5709(7)Å, ɑ = 100.870(1)°, β = 93.677(1)°, ɣ = 90.041(1)°, Z = 2, R₁ = 0.0293) was grown as large crystals from reactions of boron and carbon in
cerium/cobalt eutectic melts. The structure of the cerium-rich product features Co₄ squares capped by borocarbide chains. Magnetic studies show a ferromagnetic transition at 10 K and also
indicate fluctuating cerium valence. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of
Philosophy. / Fall Semester 2015. / November 4, 2015. / Includes bibliographical references. / Susan Latturner, Professor Directing Dissertation; Bruce Locke, University Representative; Michael Shatruk, Committee Member; Albert Stiegman, Committee
Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_291285 |
| Contributors | Zhou, Sixuan (authoraut), Latturner, Susan (professor directing dissertation), Locke, Bruce R. (university representative), Shatruk, Mykhailo (committee member), Stiegman, Albert E., 1953- (committee member), Florida State University (degree granting institution), College of Arts and Sciences (degree granting college), Department of Chemistry and Biochemistry (degree granting department) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource (103 pages), computer, application/pdf |
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