An Antiferro-to-Ferromagnetic Transition in EuTiO_3–xH_x Induced by Hydride Substitution

Abstract

We have prepared the oxyhydride perovskite EuTiO(3-x)H(x) (x ≤ 0.3) by a low temperature CaH2 reduction of pyrochlore Eu2Ti2O7 and perovskite EuTiO3. The reduced EuTiO(3-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 EuTiO(3-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 TC 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 Eu(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.

Reduction of Ln2Ti2O7 Layered Perovskites: A Survey of the Anionic Lattice, Electronic Features, and Potentials

“…Sm, Eu), the transformation into ABO 3 perovskite was reported, 8 while more recent investigation of the reduction for Eu indicated the formation of perovskite oxyhydrides EuTiO 3−x H x (x ≤ 0.3). 10 To the best of our knowledge, no significant result has been obtained for layered perovskites. La Ti O is a ferroelectric compound well known for its high Curie-temperature, spontaneous polarization and dielectric constant (T c ~ 1500 °C, Ps ~ 5 µC.cm -2 , ε ~ 42-62).…”

“…31 The complete absence of any absorption in the , CaTi(O,H) 3 , SrTi(O,H) 3 and the related solid solutions 33 and EuTi(O,H) 3 . 10 In these phases the maximal reported H ratio is shown in Figure 4 A rough estimation of the titanium redox can be deduced from the TGA under air for LTO-CaH 2 and LTO-H 2 by analogy with TGA under argon, see Fig. 3b.…”

Unconventional Luminescent Centers in Metastable Phases Created by Topochemical Reduction Reactions

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Previous efforts have focused on the investigation of magnetic compounds containing transition-metal ions, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]19] and little attention has been paid to materials containing rare-earth ions. [18] As far as we are aware,t he use of topochemical reaction for the controlled synthesis of functional materials containing heavier p-block metal ions has never been explored.Novel luminescent materials emitting in the near-infrared (NIR) spectral region are urgently needed in connection with applications for bioimaging and telecommunications.L uminescent materials containing bismuth, one of the most investigated p-block elements,h ave attracted significant research interest owing to their importance in both fundamental science and practical applications for solid-state lighting, bioimaging,l asers,a mplifiers,a nd detectors. [20][21][22][23][24] Thec omplex photophysical behaviors exhibited by various Bi-containing material systems can be attributed to the di...…”

“…Abstract: Al ow-temperature topochemical reduction strategy is used herein to prepare unconventional phosphors with luminescence covering the biological and/or telecommunications optical windows.This approach is demonstrated by using Bi III -doped Y 2 The development of functional materials has long benefited from advances in synthetic strategies.A si sw ell known, conventional high-temperature synthetic routes can be used to prepare ab road spectrum of complex oxides with thermodynamically stable phases,p recluding the formation of metastable materials.Inmarked contrast, low-temperature topochemical reduction reactions have allowed the preparation of complex transition-metal-oxide phases bearing highly unusual oxidation states and coordination geometries,attracting tremendous attention in the field of solid-state chemistry. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] Theprinciple advantage of this "soft" chemical route lies in the fact that it is driven by kinetics,t hus allowing rational design of structures and compositions as metastable products at considerably lower reaction temperatures than when conventional techniques are used. To date,aseries of material systems,such as LaNiO 2 ,SrFeO 2 ,LaSrCoO 3 H 0.7 ,and BaTiO 3Àx H x ,h ave been prepared through this route.…”

The role of oxygen vacancies on the vibrational motions of hydride ions in the oxyhydride of barium titanate

“…Perovskite-type oxyhydrides ATiO 3Àx H x (A ¼ Ba, Sr, Ca, x < 0.6), in which some of the oxide ions are replaced by hydride ions, have recently emerged as a novel class of mixed electronic-ionic conductors with potential application in energy storage and conversion. [1][2][3] Understanding the defect chemistry and hydride ion conduction mechanism in these materials is of great importance for developing efficient synthesis routes that allow the development of new oxyhydrides with tailored ionic and electronic conductivity for certain applications, but neither the defect chemistry nor hydride ion conduction mechanism are fully understood. Recent results from quasielastic neutron scattering (QENS), 4 isotope exchange, 5,6 combined isotope exchange with depth proling analysis 7 and rst-principles calculations 7,8 suggest a vacancy-assisted diffusion mechanism.…”