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RESEARCH AND DEVELOPMENT OF YTTRIUM IRON GARNET SINGLE CRYSTALS
TEXAS INSTRUMENTS INC DALLAS
Yttrium iron garnet YIG single crystals 14 to 38 in. diameter with a dielectric constant of about 10 and 0.002 dissipation factor have been produced by the floating zone technique. Ferrimagnetic resonance line-widths of less than 2 oersteds were obtained from polished test spheres. Thermal cracking remains a major problem in growing YIG crystals by the floating zone method. A calcia-stabilized ZrO2 susceptor was placed on a MoSi2 auxiliary susceptor to decrease the thermal gradient just below the molten zone however, the resultant decrease was insufficient to eliminate thermal cracks. Various arrangements and combinations of work coil, susceptor, auxillary susceptor, and auxiliary resistance heater were used to give a temperature profile along the axis of the zoned YIG that would prevent formation of thermal cracks. Although the amount of cracking was reduced, it was not completely eliminated. Analytical results given compare the impurity concentration of YIG crystals grown in the old and the new floating zone apparatus. Representative values of ferrimagnetic resonance line-width obtained from polished spheres of single crystal YIG are presented. Author