Magnetic properties of Gd2 O3

Polarized-neutron experiments have been used to measure the temperature dependence of the susceptibility of the ${\mathrm{Gd}}^{3+}$ ion at the two different crystallographic sites in cubic ${\mathrm{Gd}}_{2}$${\mathrm{O}}_{3}$ in the paramagnetic state. Below 10\ifmmode^\circ\else\textdegree\fi{}K these susceptibilities are quite different because of the different net exchange interactions with the rest of the crystal. The temperature dependences of the first- and second-neighbor spin correlations have also been observed through measurement of the diffuse scattering of unpolarized neutrons. An approximate theory of the magnetic behavior of ${\mathrm{Gd}}_{2}$${\mathrm{O}}_{3}$ in the paramagnetic region is presented which provides predictions of the susceptibilities, spin correlations, and specific heat which are in reasonable accord with experimental results. The previously reported paramagnetic form factor for ${\mathrm{Gd}}_{2}$${\mathrm{O}}_{3}$ has been revised slightly, leading to the conclusion that there is no convincing evidence supporting a difference in the $4f$ spin density between the metallic and oxide cases.