An Antiferro-to-Ferromagnetic Transition in EuTiO sub(3-x)H sub(x) Induced by Hydride Substitution

We have prepared the oxyhydride perovskite EuTiO sub(3-x)H sub(x) (x [< or =] 0.3) by a low temperature CaH sub(2) reduction of pyrochlore Eu sub(2)Ti sub(2)O sub(7) and perovskite EuTiO sub(3). The reduced EuTiO sub(3-x)H sub(x) crystallizes in the ideal cubic perovskite (Pm3m), where O/H anions are randomly distributed. As a result of electron doping by the aliovalent anion exchange, the resistivity of EuTiO sub(3-x)H sub(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 sub(C) of 12 K is higher than those of any other EuTiO sub(3)-derived ferromagnets. The ferromagnetism can be explained by the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between the Eu super(2+) 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.