Title: Reversible Hydrogen-Induced Phase Transformations in La _0.7 Sr _0.3 MnO ₃ Thin Films Characterized by In Situ Neutron Reflectometry

Abstract

Here we report on the mechanism for hydrogen-induced topotactic phase transitions in perovskite (PV) oxides using La_0.7Sr_0.3MnO₃ as a prototypical example. Hydrogenation starts with lattice expansion confirmed by X-ray diffraction (XRD). The strain- and oxygen-vacancy-mediated electron-phonon coupling in turn produces electronic structure changes that manifest through the appearance of a metal insulator transition accompanied by a sharp increase in resistivity. The ordering of initially randomly distributed oxygen vacancies produces a PV to brownmillerite phase (La_0.7Sr_0.3MnO_2.5) transition. This phase transformation proceeds by the intercalation of oxygen vacancy planes confirmed by in situ XRD and neutron reflectometry (NR) measurements. Despite the prevailing picture that hydrogenation occurs by reaction with lattice oxygen, NR results are not consistent with deuterium (hydrogen) presence in the La_0.7Sr_0.3MnO₃ lattice at steady state. The film can reach a highly oxygen-deficient La_0.7Sr_0.3MnO_2.1 metastable state that is reversible to the as-grown composition simply by annealing in air. Theoretical calculations confirm that hydrogenation-induced oxygen vacancy formation is energetically favorable in La_0.7Sr_0.3MnO₃. The hydrogenation-driven changes of the oxygen sublattice periodicity and the electrical and magnetic properties similar to interface effects induced by oxygen-deficient cap layers persist despite hydrogen not being present in the lattice.

Authors:

Mazza, Alessandro R.  ^[1];

• Search DOE PAGES for author "Mazza, Alessandro R."
• Search DOE PAGES for ORCID "0000-0002-7206-1334"

Lu, Qiyang  ^[1];

• Search DOE PAGES for author "Lu, Qiyang"
• Search DOE PAGES for ORCID "0000-0002-9155-3684"

Hu, Guoxiang ^[2]; Li, Haoxiang ^[1]; Browning, James F. ^[3]; Charlton, Timothy R. ^[3]; Brahlek, Matthew ^[1]; Ganesh, Panchapakesan  ^[4];

• Search DOE PAGES for author "Ganesh, Panchapakesan"
• Search DOE PAGES for ORCID "0000-0002-7170-2902"

Ward, Thomas Zac  ^[1];

• Search DOE PAGES for author "Ward, Thomas Zac"
• Search DOE PAGES for ORCID "0000-0002-1027-9186"

Lee, Ho Nyung  ^[1];

• Search DOE PAGES for author "Lee, Ho Nyung"
• Search DOE PAGES for ORCID "0000-0002-2180-3975"

Eres, Gyula  ^[1]

• Search DOE PAGES for author "Eres, Gyula"
• Search DOE PAGES for ORCID "0000-0003-2690-5214"

---

+ Show Author Affiliations

1. Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
2. Department of Chemistry and Biochemistry, Queens College, City University of New York, Queens, New York 11367, United States
3. Neutron Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States
4. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States

Publication Date:

Wed Feb 16 00:00:00 EST 2022

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1971396

Alternate Identifier(s):

OSTI ID: 1854458

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Published Article

Journal Name:

ACS Applied Materials and Interfaces

Additional Journal Information:

Journal Name: ACS Applied Materials and Interfaces Journal Volume: 14 Journal Issue: 8; Journal ID: ISSN 1944-8244

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; correlated oxides; LSMO; oxygen vacancy; neutron reflectometry; phase transformations; reduction reaction; hydrogenation