When a TbFe layer is so thin that the incident light transmits through several TbFe layers in a TbFe/SiO compositionaliy modulated film, a multi-reflection occurs at each interface. Kerr rotation angle can be strongly enhanced by the interference of these reflected lights. Kerr rotation angle runs up to 12 degrees at a wavelength of light of 6328Å. A large enhancement of Kerr rotation angle is attained at an arbitrary wavelength of visible light by selecting the thickness of each layer. The perpendicular magnetic anisotropy is dominant in a TbFe/SiO compositionaliy modulated film even when the thickness of a TbFe layer is 39Å because of magnetostriction at interfaces. In a compositionaliy modulated film, optical constants of a magnetic thin film, but not of a coating layer, can be tuned to the antireflection whithout quenching the perpendicular magnetic anisotropy.
