The stoichiometric antiferromagnetic insulator ${\mathrm{EuTiO}}_3$ is proximate to a ferroelectric phase. Whereas cation substitution has been used as a tuning parameter to introduce charge carriers and manipulate the magnetism, the effects of oxygen-vacancy doping have been less explored. Here we report a detailed study of the charge transport and magnetic properties of metallic, oxygen-vacancy-doped $\mathrm{EuTi}{\mathrm{O}}_{3-\delta }$. Using ${\mathrm{CaH}}_2$ as an oxygen getter to achieve a higher carrier concentration than previously reported, we find that the phase diagram of the oxygen-vacancy-doped system is distinct from that obtained via cation doping. In particular, we uncover a change from antiferromagnetic to ferromagnetic order in the metallic state, with a maximum Curie temperature of $T_C \approx 11$ K at the highest carrier concentration of $n \approx {10}^{21}\mathrm{c}{\mathrm{m}}^{-3}$. These findings are supported by density functional theory calculations, which indicate a significant change in the nearest-neighbor magnetic exchange constant with increasing electron doping. We also present x-ray diffuse scattering and complementary first-principles results that reveal that, similar to the prominent incipient ferroelectric perovskite ${\mathrm{SrTiO}}_3$, the data for as-grown ${\mathrm{EuTiO}}_3$ are consistent with thermal diffuse scattering and with the absence of quasielastic contributions. For oxygen-vacancy-doped $\mathrm{EuTi}{\mathrm{O}}_{3-\delta }$, the x-ray data reveal a lower cubic-tetragonal transition temperature and additional short-range correlations at low temperatures. Finally, we report specific heat measurements that confirm the magnetic transition temperatures deduced from magnetization measurements and corroborate the lattice dynamics picture inferred from the diffuse scattering data.

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• Doping effects
• Ferroelectricity
• Magnetic order
• Magnetic phase transitions
• Spin-orbit coupling
• Perovskites
• Density functional theory
• Resistivity measurements