Nuclear Magnetic Resonance Studies of Some Materials Containing Divalent Europium

This paper reports the results of a low-temperature NMR experiment on Eu¹⁵³ in EuO. The data, which are assumed to be linear with magnetization, are compared with calculated values using spin-wave theory. Values of J₁kb=0.750±0.0025^∘K and J₂kb=-0.0975±0.004^∘K are found to give a good description of EuO. This paper also reports the results of NMR studies of the ligands F¹⁹ and Cs¹³⁷ in EuF₂ and CsEuF₃. 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 Gd³⁺ and in terms of a virtual $5d$ state in Eu²⁺.