This paper presents a model for the unsteady species transport during bulk growth of alloyed semiconductor crystals with both axial and transverse magnetic fields. During growth of alloyed semiconductors such as germanium-silicon (GeSi) and mercury-cadmium-telluride (HgCdTe), the solute's concentration is not small so that density differences in the melt are very large. These compositional variations drive compositionally-driven buoyant convection, or solutal convection, in addition to thermally-driven buoyant convection. These buoyant convections drive convective transport which produce non-uniformities in the concentration in both the melt and the crystal. This transient model predicts the distribution of species in the entire crystal grown in a magnetic field. The present study investigates the effects of magnetic field orientation and strength on the segregation in alloyed semiconductor crystals, and presents results of concentration in the crystal and in the melt at several different times during crystal growth. (C) 2004 Elsevier Ltd. All rights reserved.