Excited configurations of hydrogen in the BaTiO${}_{3-x}$H${}_x$ perovskite lattice associated with hydrogen exchange and transport

Abstract

Excited configurations of hydrogen in the oxyhydride BaTiO${}_{3-x}$H${}_x$ ($x=0.1-0.5$), which are considered to be involved in its hydrogen transport and exchange processes, were investigated by positive muon spin relaxation (${\mu }^{+}$SR) spectroscopy using muonium (Mu) as a pseudoisotope of hydrogen. Muons implanted into the BaTiO${}_{3-x}$H${}_x$ perovskite lattice were mainly found in two qualitatively different metastable states. One was assigned to a highly mobile interstitial protonic state, which is commonly observed in perovskite oxides. The other was found to form an entangled two spin-$\frac{1}{2}$ system with the nuclear spin of an H${}^{-}$ ion at the anion site. The structure of the (H,Mu) complex agrees well with that of a neutralized center containing two H${}^{-}$ ions at a doubly charged oxygen vacancy, which was predicted to form in the SrTiO${}_{3-\delta }$ perovskite lattice by a computational study [Y. Iwazaki $et$ $al$., APL Materials 2, 012103 (2014)]. Above 100 K, interstitial Mu${}^{+}$ diffusion and retrapping to a deep defect were observed, which could be a rate-limiting step of macroscopic Mu/H transport in the BaTiO${}_{3-x}$H${}_x$ lattice.

5 pages, 4 figures

References in corpus (1)

• Muon-fluorine entangled states in molecular magnets

Cited by in corpus (7)

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