A magnetic field of H=10T was applied perpendicularly or parallel to the surface of the 30BaO.15TiO2.55GeO2 (BTG) glass during its crystallization, and the effect of the magnetic field on the crystal orientation and second-order optical nonlinearity of the Ba2TiGe2O8 crystals formed at the glass surface was examined. Compared with the sample prepared by conventional crystallization in zero magnetic field, the c-axis (polarization axis) orientation and second-harmonic intensity of the Ba2TiGe2O8 crystals at the surface were enhanced in the sample fabricated with the field perpendicular to the surface and, by contrast, were depressed in the sample fabricated with the field parallel to the surface. The present study indicates that the application of high magnetic fields during crystallization is a technique to control the crystal orientations and optical properties of BTG crystallized glasses.

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A high magnetic field of H = 10 T was applied to 30BaO-15TiO2-55GeO2 glass through its crystallization process. It was found that the c-axis of Ba2TiGe2O8 optical nonlinear/ferroelectric crystals oriented along the magnetic field. The second harmonic intensity of crystallized glass which the high magnetic field was applied perpendicular to the surface of glass was enhanced compared with a conventional crystallization in no magnetic field. Transparencies, photorefractive indices and thicknesses were also measured. As a result, crystal orientation of Ba2TiGe2O8 in glass matrix induced by a high magnetic field causes improvement of transparency and low value of photorefractive index.