Characterization of the growth mechanism of YIG crystal fibers using the laser heated pedestal growth method

Yttrium iron garnet (YIG, Y3Fe5O12) single-crystal fibers were grown by the laser heated pedestal growth (LHPG) method. Different compositions, with various Y2O3 and Fe2O3 ratios seeds were used. The microstructure and the compositional variation of the obtained crystals show that YIG single-crystal fibers could be directly grown at the stable freezing interface when the melt had a composition of 78-87 mol% Fe2O3. When the seed's Fe2O3 concentration was below 78 mol%, the yttrium orthoferrite (YFeO3) would crystallize out until the composition of the melt increased along the liquidus curve until it needed a concentration of 78 mol% Fe2O3 or higher, whereupon YIG started to crystallize from the liquid. With the LHPG method, however, when Fe-rich ceramic rod used as a seed was employed to grow YIG crystal, the crystallographic orientation was indefinite. Therefore, YIG single-crystal fibers with the desired crystallographic orientation could only be obtained using a two-pass method. During the forward pass, YIG single crystal could be directly grown using a Fe-rich solvent, while during the backward pass, the crystallographic orientation of the grown crystal would be the same as that of the YIG seed.