An Antiferro-to-Ferromagnetic Transition in EuTiO_3–<i>x</i>H_<i>x</i> Induced by Hydride Substitution

Abstract

We have prepared the oxyhydride perovskite EuTiO_3–<i>x</i>H_<i>x</i> (<i>x</i> ≤ 0.3) by a low temperature CaH₂ reduction of pyrochlore Eu₂Ti₂O₇ and perovskite EuTiO₃. The reduced EuTiO_3–<i>x</i>H_<i>x</i> crystallizes in the ideal cubic perovskite (<i>Pm</i>3̅<i>m</i>), where O/H anions are randomly distributed. As a result of electron doping by the aliovalent anion exchange, the resistivity of EuTiO_3–<i>x</i>H_<i>x</i> shows metallic temperature dependence. Moreover, an antiferromagnetic-to-ferromagnetic transition is observed even when a small amount of hydride (<i>x</i> ∼ 0.07) is introduced. The Curie temperature <i>T</i>_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