Bi3+-doped iron garnet crystals (Bi:RIG) have received extensive attention for their excellent magneto-optical properties. The quality of garnet crystals has a great relationship with mismatch in the lattice and thermal expansion between crystals and seeds. Compared with TGG seeds, Sc,Ga:YIG is more suitable as the seed for growing Bi:(HoEu)IG crystals. The crystal quality and match in the lattice and thermal expansion have been discussed. The as-grown Bi:(HoEu)IG crystal has a specific Faraday rotation angle of −467° cm–1 and shows a strong magneto-optical effect.