Onset of valence and magnetic instabilities in the ferromagnetic semiconductor EuO at high pressures

Hydrostatic high-pressure ¹⁵¹Eu M\"ossbauer measurements (0{≤}p{≤}31 GPa) on the ferromagnetic semiconductor EuO reveal, contrary to previous suggestions, no pronounced valence change of Eu (Eu²⁺{→}Eu³⁺) even at highest pressures (p=31 GPa). The magnetic ground state becomes unstable above 23 GPa, where the pressure-induced variation of the Curie temperature is consistent with theoretical predictions based on the volume-dependent competition between sf-exchange interactions and sf hybridization.