Two Bi12SiO20 single crystals empty set10 x 30 mm(2) were grown with and without a rotating magnetic field by the vertical zone-melting technique. Growth striations are completely absent and defects almost could not be found inside the crystal grown with a rotating magnetic field, while striations and numerous defects could be found inside the single crystal grown without a rotating magnetic field. The mechanism of effect of a rotating magnetic field on the growth of Bi12SiO20 crystals is tentatively proposed so that the rotating magnetic field induces a current and consequently generates a forced convection in the melt. If a steady, axisymmetric and desirable convection is generated by the applied rotating magnetic field, the transport of heat and mass in the melt near the crystal-melt interface is enhanced and maintains stability. As a result, the crystallographic perfection and homogeneity of the grown crystal could be significantly improved by using a rotating magnetic field combined with the vertical zone-melting technique. (C) 2010 Elsevier B.V. All rights reserved.