Abstract
The change of the N\'eel temperature of europium metal and of the Curie temperature of EuO with pressure has been measured up to 90 kbar by resistivity and initial-permeability methods, respectively. The compressibility of Eu and EuO has been determined relative to NaCl in the same range of pressure by powder x-ray diffraction methods. The compressibility is represented by the Birch equation; for Eu ${B}_{0}=124$ kbar and $\ensuremath{\xi}=0.9 (\frac{d{\ensuremath{\beta}}_{0}}{\mathrm{dp}}=2.8)$ and the standard deviation is 1.8; for EuO, ${B}_{0}=1070$ kbar and $\ensuremath{\xi}$ was assumed to be zero and the standard deviation is 2.8. For Eu, $d\mathrm{ln}\frac{{T}_{N}}{d}\mathrm{ln}V\ensuremath{\approx}0$ down to $\frac{V}{{V}_{0}}=0.8$. The initial slope for EuO is $d\mathrm{ln}\frac{{T}_{c}}{d}\mathrm{ln}V=\ensuremath{-}6\ifmmode\pm\else\textpm\fi{}2$. The results are discussed in terms of the theories of exchange interaction in the heavy rare-earth metals and the europium chalcogenides.
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