Magnetic Study of the Lighter Rare-Earth Ions in the Iron Garnets

The magnetic behavior of the trivalent ions of La, Pr, Sm, and Eu in the iron garnets in the range 0 to 298°K has been determined, that of the ${\mathrm{Nd}}^{3+}$ ion having been reported earlier. The diamagnetic ion ${\mathrm{La}}^{3+}$ behaves similarly to ${\mathrm{Y}}^{3+}$. An applied field of about 70 kOe appears to produce magnetic saturation of {${\mathrm{Y}}_2$Pr} ${\mathrm{Fe}}_2$ ${\mathrm{Fe}}_3$ ${\mathrm{O}}_{12}$ at 4.2°K, the contribution of the ${\mathrm{Pr}}^{3+}$ ion being 1.6 ${\mathrm{\mu }}_{\mathrm{B}}$ at this temperature. The ${\mathrm{Sm}}^{3+}$ ion introduces large anisotropy but spherical crystals of samarium iron garnet allowed to move freely in the applied field lead to saturation at relatively low fields. The ${\mathrm{Sm}}^{3+}$ ion contributes a moment of 0.14 ${\mathrm{\mu }}_{\mathrm{B}}$ at 0°K to the net magnetization and behaves similarly to the ${\mathrm{Pr}}^{3+}$ and ${\mathrm{Nd}}^{3+}$ ions at temperatures below 298°K in that its moment adds to that of the resultant of the iron sublattice moments. Results of measurements of a single-crystal sphere of europium iron garnet are in agreement with those made on a polycrystalline specimen by Villers et al.