The effects of adding Ti to TbFe and TbFeCo films with and without protective layers were studied. The addition of Ti improved the corrosion resistance of the films. The transmittance of TbFeCo films was reduced by a factor of 10 by the substitution of 5% Ti for Fe, and by a factor of 100 by the substitution of 10% Ti for Fe. Pit formations in TbFeCo during aging in a corrosive condition and immersion in a NaCl solution were almost completely eliminated by the substitution of 5% Ti for Fe. The Kerr rotation angle (&thgr;k) decreased slightly in TbFeCo by the substitution of 10% Ti for Fe, while improving the corrosion resistance.