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|Title:||Synthesis, Structural and Magnetic Properties of Rare-Earth Intermetallic Compounds|
|Authors:||Cheung, Yan Yin Janice|
|Keywords:||Inorganic Chemistry;Materials Chemistry;Inorganic Chemistry|
|Abstract:||<p>Series of rare-earth intermetallic compounds were synthesized and studied.</p> <p>The Gd<sub>4</sub>Ge<sub>3-<em>x</em></sub><em>Pn<sub>x</sub></em> (<em>Pn</em> = P, Sb, Bi; <em>x</em> = 0.5 - 3) series of compounds were synthesized to explore the stability of the non-existent Gd<sub>4</sub>Ge<sub>3</sub> binary through partial <em>Pn</em> substitutions to increase valence electron concentrations. Electronic band structure calculations were performed to elucidate the relationships between the hypothetical "Gd<sub>4</sub>Ge<sub>3</sub>" and Gd<sub>5</sub>Ge<sub>4</sub> binaries. All Gd<sub>4</sub>Ge<sub>3-<em>x</em></sub><em>Pn<sub>x</sub></em> phases order ferromagnetically with relatively high Curie temperatures of 234 to 356 K.</p> <p>The Gd<sub>5</sub>Ge<sub>4-<em>x</em></sub>P<em><sub>x</sub></em> phases were synthesized to explore the effects of both atomic size and valence electron concentration differences between Ge and P atoms. Partial substitution of P for Ge atoms occur on the interslab site, which causes the interslab distances to increase. In Gd<sub>5</sub>Ge<sub>4-<em>x</em></sub>P<em><sub>x</sub></em>, only a small amount of P substitution (<em>x</em> = 0.25) is required to induce ferromagnetic ordering. The appearance of a Griffiths phase is also discussed.</p> <p>The temperature dependence of the different <em>RE</em><sub>2</sub>Fe<sub>17</sub> (<em>RE</em> = Gd - Ho) phases was tracked by reciprocal space images generated from single crystal X-ray diffraction.</p> <p>GdCo<sub>4</sub>B was synthesized by arcmelting and tri-arc techniques to confirm the presence of magnetostriction. Single crystal and powder X-ray diffraction, dilatometer and magnetic measurements were done.</p>|
|Appears in Collections:||Open Access Dissertations and Theses|
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