SYNTHESIS OF NONTHERMODYNAMICAL Bi_3Fe_5O_<12> SYSTEM WITH PROMINENT MAGNETOOPTICAL CHARACTERISTICS

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(1)Studies on improvement of film quality of pure Bi_3Fe_5O_<12> garnet(1)Precise XRD measurements were done on the polycrystalline Bi_3Fe_5O_<12> (BIG) film specimens prepared using newly developed technique. A trace of Bi_2Fe_4O_9 was found in both single-and poly-crystalline BIG films. From symmetric and asymmetric XRD measurements, the precise lattice parameter of BIG was determined as 1.2647nm which is much larger than the value of 1.2624nm determined on the single crystalline film specimen or extrapo lated from Bi-substituted YIG system. The thermodynamical garnet layr for epitaxial growth substrate showed no specific orientation, however, polycrystalline BIG layr [100] orientation along the film normal.(2)A role of Bi^<3+> ion in magnetic and magnetooptical properties of BIG were studied by measuring Faraday rotation angle rheta_F at 633nm and room temperature applying the magnetic field upto 150T.The Faraday effect of BIG under higher magnetic field was found to be strongly affected by electronic charge transfer at the tetrahedral site.(2)Studies on ionic subtitution effects in BIGIn BIG,the ions which are easily substituted in the thermodynamical garnets, such as Al^<3+> or Ga^<3+>, were diffused readily during the film growth and substituted uniformly. Co^<2+> ions which is hardly substituted in the thermodynamical garnet was also hardly introduced into the lattice sites in BIG.Co^<2+> ions were found to exist as very fine particles of Co_XFe_<3-X>O_4 spinel phase which were magnetically coupled with BIG by exchange interaction. The alternating ion beam sputtering technique was proved to be very effective for not only ion substitution but also creation of new composite materials.