Optical Floating Zone Method Preparation And Characterization Of GdFeO3Single Crystal

Magneto-optical material is considered as a kind of functional material with magneto optical effects. A variety of optical devices have been designed using the magneto-optical effects, such as modulator, isolator, optical switch, sensor, storage, display, etc. With the fast development of optical fiber communication, optical information processing and integrated optical industry, the demand for magneto-optical material and devices are increasing and the requirement are becoming more rigorous. In the near infrared region, YIG and other rare earth substituted crystals are mainly applied in optical devices, including isolator, switch and deflector which show practical applications in the field of optical fiber communications. Recently, in order to meet the demand of miniaturized and integrated magneto-optical devices, the material with fast response and high sensitivity are greatly preferred. GdFeO3single crystal has gained considerable interest due to its high magneto-optical figure of merit in near infrared range and the highest domain wall motion velocity.The natural materials are mostly in the form of microcrystal. The single crystals as large as natural gems are minimal. Therefore, the development and application history of crystals is much shorter than that of polycrystals. Because of the single crystals scarcity in nature and demands for people, so people actively exploring the artificial method of synthesis and growth new crystals. GdFeO3single crystal congruently melts at1700℃. However, many difficulties are encountered in growing high quality GdFeO3single crystal. In the past decades, several methods have been reported to grow GdFeO3crystal, such as flux method, hydrothermal method and LPE method. But the crystals are still suffered from many kinds of defects. Based on the optical floating zone method, the thesis is mainly conducted in the following sections: the preparation of GdFeO3powder and polycrystalline rod, crystal growth, analysis of defects and the characterization of magnetic properties. The feed rods for crystal growth were prepared by solid-state reaction and sol-gel combustion, respectively. In sol-gel combustion, the powder has smaller size and better sinterability, lowering the sintering temperature to1400℃. The optical floating zone growth of GdFeO3has been systematically investigated. The crystal has been both grown by spontaneous nucleation and seeds. These factors that influence the growth results includes the shape and stability of the molten zone, the quality of the feed rod, the temperature distribution, growth rate, rotating rate and shape of solid-liquid interface. All of these factors have been intensively discussed, and the optimized conditions of the growth parameters have been obtained. Finally, GdFeO3single crystal with high quality has been successfully grown by optical floating zone method.Several kinds of defects in GdFeO3crystal has been studied, such as growth striations, cracking, dislocations and voids. The formation mechanisms of these defects were discussed and the relevant approaches of restraining these defects have also been presented. The investigation of the growth defects is essential to optimize the growth parameters and improve crystal quality. At the same time use X-ray direction finder set a, b, c in three directions, and to analyze the magnetic properties of GdFeO3single crystal.