PRODUCTION METHOD FOR Bi-SUBSTITUTED RARE-EARTH IRON GARNET SINGLE CRYSTAL MEMBRANE FOR MAGNETO-OPTI

PROBLEM TO BE SOLVED : To provide a magneto-optical element which has a RIG membrane with a low insertion loss at an optocommunication wave length of 1.3-1.6 μm; and a method for stably producing the RIG membrane for a magneto-optical element with a high yield by using an LPE method. SOLUTION : A specified amount of an impurity is added to a melt so that Fe present in a RIG membrane after its growth is substantially trivalent and tetravalent (or divalent) and is not made divalent (or tetravalent) by a heat treatment conducted after the growth. After the above addition of the impurity, a RIG membrane is grown from the melt on a nonmagnetic garnet substrate by a liquid-phase epitaxial method. Then, the nonmagnetic garnet substrate is removed, and the RIG membrane is heat treated in a reducing (or oxidizing) atmosphere.