PURPOSE: To reduce the magnetism resistant force by annealing a liquid-phase Ga epitaxial film containing Bi ions Bi3+ at a 24C position at 800°C or more.

CONSTITUTION: A liquid-phase Ga epitaxial film containing Bi ions Bi3+ at a 24C position is annealed at a temperature of 800°C or more. The magnetism resistant force of a Bi substituted liquid-phase epitaxial layer is generally high. The magetism resistant force by a magnetic domain modulating method using an AC magnetic field in the liquid-phase Ga epitaxial film of Tm2.4Bi0.6Fe3.85Ga1.15O12 is 2.5 Oe. In the case the magnetism resistant force is large as mentioned above, there is a drawback that the printing pattern is remained even after the magnetic tape has been removed from the Ga film. The large magnetism resistant force of Bi substituted Ga is caused by irregular placement of the Bi ion Bi3+ whose radius is large at the position 24C of a Ga lattice and by partial distortion of the lattice. Such distortion can be eliminated by the annealing, thereby the magnetism resistant force can be reduced.