The magnetostriction constants &lgr;100and &lgr;111have been measured at room temperature for YIG single crystals in which a small fraction of the iron ions are replaced by silicon. The magnetically active impurity is believed to be divalent iron which compensates the Si4+. As the silicon concentration reaches about 0.05 Si atoms/Y3Fe5O12, both &lgr;'s pass through zero. In crystals of this composition the magnetization is largely decoupled from the strain distribution in the crystal. A peak in low‐frequency permeability and simple easily interpreted domain structures correspond to this &lgr; = 0 composition.