Magnetic Susceptibilities of Cubic Mixed Europium Oxides

The magnetic susceptibility $\chi$ of polycrystalline cubic solid solutions of ${\mathrm{Eu}}_2$${\mathrm{O}}_3$ with ${\mathrm{Y}}_2$${\mathrm{O}}_3$, and ${\mathrm{Gd}}_2$${\mathrm{O}}_3$ have been measured. The $\chi$ of ${\mathrm{Eu}}^{3+}$ in ${\left({\mathrm{Eu}}_x{\mathrm{Y}}_{1-x}\right)}_2{\mathrm{O}}_3$ increases with decreasing concentration of ${\mathrm{Eu}}^{3+}$ ions, although the anisotropic exchange interaction would be expected to decrease at the same time. The $\chi$ of the smaller unit-cell compound, ${\left({\mathrm{Eu}}_{0.1}{\mathrm{Lu}}_{0.0}\right)}_2$${\mathrm{O}}_3$, yields an even higher value for the $\chi$ of ${\mathrm{Eu}}^{3+}$ than do the Eu-Y mixed oxides, indicating a strong dependence of the crystal-field parameters on the unit-cell dimension. In ${\left({\mathrm{Eu}}_x{\mathrm{Gd}}_{1-x}\right)}_2{\mathrm{O}}_3$ the $\chi$ of ${\mathrm{Eu}}^{3+}$ has the same value as in ${\mathrm{Eu}}_2$${\mathrm{O}}_2$ for all values of $x$ while the $\chi$ of ${\mathrm{Gd}}^{3+}$ is given by $\chi =\frac{C}{\mathrm{}[T+(1-x\left)\mathrm{}\theta \right]}$.