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Title:	Physical, magnetic and magneto-optical properties of terbium yttrium iron garnets and terbium aluminium yttrium iron garnets sol-gel films
Authors:	Ftema W. Abdalhade (P47380)
Supervisor:	Noor Baayah Ibrahim, Prof. Dr
Keywords:	Magnetic Magneto-optical Yttrium iron garnets Ferrites (Magnetic materials)
Issue Date:	22-Jan-2013
Description:	Terbium yttrium iron garnet films with composition of TbxY3-xFe5O12 (0≤x≤3) and terbium aluminium yttrium iron garnet films Tb0.8Y2.2AlyFe5-yO12 (0≤y≤1) were prepared by sol-gel method followed by the spin coating technique. The annealing process was carried out at 700, 800 and 900 °C for the Tb-YIG film and 900 °C for the TbAl-YIG films. The films were deposited onto quartz substrate using spin coating technique. Microstructural characterization using X-ray diffraction (XRD) showed that the TbxY3-xFe5O12 films exhibited a pure single phase of garnet structure at annealing temperature of 900 °C. Furthermore, at this temperature the shift of the peak in the patterns towards low angle was observed indicating the incorporation of Tb3+ in the YIG structure. At 700 and 800 °C, few peaks of garnet mixed with a minute quantity of Fe2O3, YFeO3 and magnetite were observed due to the inadequate annealing temperature to crystalline the films. The lattice parameter of the Tb-YIG films was found to increase with increasing annealing temperature. The lattice parameter increases with the Tb3+content (x) due to the bigger ionic radius of the Tb3+ ion compared with the ionic radius of Y3+ ion. The surface morphology and the grains sizes were measured using a field emission scanning microscope (FE-SEM). The grain size increased with increasing annealing temperature. The film's thickness measured from the film's cross sections of FE-SEM images is smaller at 900 °C due to the densification that occurred in the films. However, the grain and the thickness of the films were independent of the Tb3+ content (x).The film's elemental components were examined by energy dispersive X-ray (EDX) which was confirmed by the presence of Tb, Y, Fe and O in the entire films. The XPS analysis for x=0.2, 0.4 and 1.5 films confirmed that the films have Tb3+, Y3+, Fe3+ and small amount of Fe2+. The magnetization measurements using a vibrating sample magnetometer (VSM) showed that the saturation magnetization (Ms) of the films increases with increasing annealing temperature due to the bigger grains sizes. The highest Ms value of 104 emu/cm3 was observed at x=1.5. However, the Ms is lower than the bulk YIG. The Ms value was also decreased with increasing of Tb3+ content. The coercivity (Hc) of the films decreases with increasing annealing temperature. The Faraday rotation (θF) of the films showed fluctuating values with increasing of annealing temperature and it has a lowest θF value at 900 °C. On the other hand, the θF of films increases with the values between -2×106 and -2.9×105 deg/cm with increasing Tb3+ content from x=0 to 3. The Tb0.8Y2.2AlyFe5-yO12 films showed single phase of garnet structure. The lattice parameter was decreased with increasing of the Al3+ content due to substitution of smaller Al3+ ions for the larger Fe3+ ions. The grains size of the films decreases up to y=0.6. The thickness of the films is variable and the highest value is observed for y=0.4 film. The Ms decreased with increasing of Al3+, but a small increase was observed when y>0.6. The coercivity decreased with increasing of Al3+ for films with values between 31.2 Oe and 47 Oe except at y=0.6 film, the Hc showed a strong increasing tendency due to the small grain size. The highest θF value was observed for y=0.4 film. However, the Tb-YIG and Tb Al YIG films were successfully prepared by sol-gel method and they have potential for microwave applications due to the low coercivity and for infrared sensor applications due to the small Faraday rotation angle in low magnetic fields.,Ph.D
Pages:	177
Call Number:	QC766.F3.A233 2013
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Science and Technology / Fakulti Sains dan Teknologi

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