Gallium-Substituted Yttrium Iron Garnet

Spontaneous moments, near 0°K, of specimens with $x$ to 3.00 in the system ${\mathrm{Y}}_3{\mathrm{Fe}}_{5-x}{\mathrm{Ga}}_x{\mathrm{O}}_{12}$ have been measured and the ionic distribution determined by means of the model given previously by Geller, Williams, Espinosa, and Sherwood. It is shown that although for $x$ to about 2.75, the preference of ${\mathrm{Ga}}^{3+}$ ions for tetrahedral sites is greater than that of ${\mathrm{Al}}^{3+}$ ions in the analogous system ${\mathrm{Y}}_3{\mathrm{Fe}}_{5-x}{\mathrm{Al}}_x{\mathrm{O}}_{12}$, for greater $x$, the preference of ${\mathrm{Ga}}^{3+}$ ions for tetrahedral sites may be the same as or less than that of ${\mathrm{Al}}^{3+}$ ions. The ${\mathrm{Ga}}^{3+}$ ion distribution in this system is such that to $x\approx 2.50$, the garnets act like ideal Néel ferrimagnets. Comparisons are made with the results of other investigations on this system.