The temperature dependence of the magneto‐optic sensitivity of gallium‐substituted yttrium iron garnets was measured at 1.3 &mgr;m and compared with a model based on molecular field theory. The model incorporates results of measurements of both the saturation magnetization and saturation Faraday rotation versus temperature. These measurements were analyzed in the context of molecular field theory to extract the fundamental molecular field coefficients and the magneto‐optical coefficients as functions of gallium content. The model and direct sensitivity measurements both indicate that the magneto‐optic sensitivity of garnet compositions with gallium substitution levels near 0.8 should exhibit a vanishing first‐order temperature sensitivity.©American Institute of Physics.