Prepared By Coprecipitation Bi Substituted Yttrium Iron Garnet Thin Films

Magneto-optical recording is the most highly developed erasable optical data storage technology. In this recording means, minimum mark length is proportional to the wavelength of the laser source, because of the diffraction limitation. So the conventional magneto-optical recording median, rare earth-transition metal (Re-Tm) alloys, is limited, because of its small Kerr rotation in the region of short wavelength. Furthermore its chemical stabilization is poor unless the films are well passivated. Bismuth substituted iron yttrium iron garnets (Bi-YIG) have a large magneto-optical (MO) effect in the region of short visible wavelength and a high corrosion resistance. Therefore it was regarded as one of the most promising next generation magneto-optical recording media, and attracted widely investigation.In the review part, I firstly discribed what is magnetooptical effect, and reviewed various magnetooptical materials. Then I emphasized on iron garnet's structure, magnetic and magneto-optic properties, the development process, and the preparation techniques. I also introduced the application of Bi-YIG as magneto-optical isolator, magneto-optical current/ magnetic field sensors, and magneto-optical recording media. Lastly I compared the different magnetooptical theoretical models.My experiments are comprized of four sections:1. Preparing Bi-YIG nano-particles by coprecipitation. The relation of PH value, milling time, and heat treatment conditions to the crystallization and size of Bi-YIG nano-particles is discussed.2. Preparing magneto-optical hybridized films by coprecipitation and spin-coationg. I studied the function of heat treatment conditions to the films' Faraday rotation, scartter coefficient, and magneto-optical merit. Under the optimized annealingcondition, the film's magneto-optical merit is as high as 4.7° , at the wavelength of 633nm. In this charpter, magneto-optical examination method is also introduced.3. Preparing nanocrystalline Bi-YIG films by pyrolyzing coprecipitated hydroxide slurry. I invented a new method to produce Bi-YIG films. By this method crystal grain size decreases to as small as 10 to 20nm. Further this method is simpler than conventional method in the coating process.4. Deposited Bi-YIG polycrystalline films by rf magnetron sputtering Bi-YIG ceramic target. By the examination of XRD, all the peaks are ascribed to the garnet phase. And the scan electronic microscopy reveals that the films are smooth dense and crack-free. These results prove that the novel target is feasible.