An Antiferro-to-Ferromagnetic Transition in EuTiO3–x H x Induced by Hydride Substitution

We have prepared the oxyhydride perovskite EuTiO3–x H x (x ≤ 0.3) by a low temperature CaH2 reduction of pyrochlore Eu2Ti2O7 and perovskite EuTiO3. The reduced EuTiO3–x H x crystallizes in the ideal cubic perovskite (Pm3̅m), where O/H anions are randomly distributed. As a result of electron doping by the aliovalent anion exchange, the resistivity of EuTiO3–x H x shows metallic temperature dependence. Moreover, an antiferromagnetic-to-ferromagnetic transition is observed even when a small amount of hydride (x ∼ 0.07) is introduced. The Curie temperature T C of 12 K is higher than those of any other EuTiO3-derived ferromagnets. The ferromagnetism can be explained by the Ruderman–Kittel–Kasuya–Yosida (RKKY) interaction between the Eu2+ spins mediated by the itinerant Ti 3d electrons. The present study shows that controlling the oxide/hydride ratio is a versatile method to tune magnetic and transport properties.