Orthoferrite Single Crystals Growing by Modified Czochralski Method and their Properties

Abstract
To obtain bulky large-sized orthoferrite single crystals with different rare-earth elements a new crystal growth technology is proposed including modified Czochralski method and using no metal crucibles for melt suspension. For this purpose two unusual Czochralski method modifications are used. In the first one the melt of crystallized material is obtained at heating the upper surface of polycrystalline block with intensive light radiation focused by 3 powerful single ellipsoidal mirror light concentrators, and in the second one the combination of surface heating with 3 intensive light concentrators and induction of high-frequency heating of the melt placed in cold crucible is used to produce it. In the last case the melt volume is considerably larger and this circumstance allows to obtain large-sized single crystals. For optimum thermal field formation needed for crystal pulling the relation between cold crucible diameter, frequency of inductive coi1 and power of the focused light inputted in the melt plays the main role. Using this technology rather perfect single crystals of yttrium, gadolinium, thulium etc. orthoferrites 25-30 mm in diameter and up to 50 mm long were grown. The maximum crystal diameter depends on the diameter of the cold crucible used and can be really increased up to 50 mm. Yttrium orthoferrite single crystals obtained by this technology have the following perfection characteristics : X-ray rocking curve width is 10" in the central part of the crystal, the dislocation density is 1-10/cm² in the central part and up to 10⁴ on the periphery, blocks and twins are absent.