Nuclear Magnetic Resonance Studies of Some Materials Containing Divalent Europium

Abstract

This paper reports the results of a low-temperature NMR experiment on ${\mathrm{Eu}}^{153}$ in EuO. The data, which are assumed to be linear with magnetization, are compared with calculated values using spin-wave theory. Values of $\frac{{J}_{1}}{{k}_{b}}=0.750\ifmmode\pm\else\textpm\fi{}0.0025\ifmmode^\circ\else\textdegree\fi{}$K and $\frac{{J}_{2}}{{k}_{b}}=\ensuremath{-}0.0975\ifmmode\pm\else\textpm\fi{}0.004\ifmmode^\circ\else\textdegree\fi{}$K are found to give a good description of EuO. This paper also reports the results of NMR studies of the ligands ${\mathrm{F}}^{19}$ and ${\mathrm{Cs}}^{137}$ in Eu${\mathrm{F}}_{2}$ and CsEu${\mathrm{F}}_{3}$. These experiments indicate that there is a reversal in sign of the unpaired spin density of the europium ion. The same results are obtained with europium-bearing glasses. This effect is discussed in terms of the Freeman-Watson model of ${\mathrm{Gd}}^{3+}$ and in terms of a virtual $5d$ state in ${\mathrm{Eu}}^{2+}$.