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Title: Interface-induced multiferroism by design in complex oxide superlattices

Abstract

Interfaces between materials present unique opportunities for the discovery of intriguing quantum phenomena. Here, we explore the possibility that, in the case of superlattices, if one of the layers is made ultrathin, unexpected properties can be induced between the two bracketing interfaces. We pursue this objective by combining advanced growth and characterization techniques with theoretical calculations. Using prototype La 2/3Sr 1/3MnO 3 (LSMO)/BaTiO 3 (BTO) superlattices, we observe a structural evolution in the LSMO layers as a function of thickness. Atomic-resolution EM and spectroscopy reveal an unusual polar structure phase in ultrathin LSMO at a critical thickness caused by interfacing with the adjacent BTO layers, which is confirmed by first principles calculations. Most important is the fact that this polar phase is accompanied by reemergent ferromagnetism, making this system a potential candidate for ultrathin ferroelectrics with ferromagnetic ordering. Monte Carlo simulations illustrate the important role of spin–lattice coupling in LSMO. These results open up a conceptually intriguing recipe for developing functional ultrathin materials via interface-induced spin–lattice coupling.

Authors:
 [1];  [2];  [3];  [4];  [1];  [1];  [3];  [5];  [5];  [1];  [4];  [6];  [1];  [1]
  1. Louisiana State Univ., Baton Rouge, LA (United States)
  2. Louisiana State Univ., Baton Rouge, LA (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. Southeast Univ., Nanjing (China). School of Energy and Environment
  4. Vanderbilt Univ., Nashville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  6. Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1376517
DOE Contract Number:
AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Proceedings of the National Academy of Sciences of the United States of America; Journal Volume: 114; Journal Issue: 26
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Guo, Hangwen, Wang, Zhen, Dong, Shuai, Ghosh, Saurabh, Saghayezhian, Mohammad, Chen, Lina, Weng, Yakui, Herklotz, Andreas, Ward, Thomas Z., Jin, Rongying, Pantelides, Sokrates T., Zhu, Yimei, Zhang, Jiandi, and Plummer, E. W.. Interface-induced multiferroism by design in complex oxide superlattices. United States: N. p., 2017. Web. doi:10.1073/pnas.1706814114.
Guo, Hangwen, Wang, Zhen, Dong, Shuai, Ghosh, Saurabh, Saghayezhian, Mohammad, Chen, Lina, Weng, Yakui, Herklotz, Andreas, Ward, Thomas Z., Jin, Rongying, Pantelides, Sokrates T., Zhu, Yimei, Zhang, Jiandi, & Plummer, E. W.. Interface-induced multiferroism by design in complex oxide superlattices. United States. doi:10.1073/pnas.1706814114.
Guo, Hangwen, Wang, Zhen, Dong, Shuai, Ghosh, Saurabh, Saghayezhian, Mohammad, Chen, Lina, Weng, Yakui, Herklotz, Andreas, Ward, Thomas Z., Jin, Rongying, Pantelides, Sokrates T., Zhu, Yimei, Zhang, Jiandi, and Plummer, E. W.. 2017. "Interface-induced multiferroism by design in complex oxide superlattices". United States. doi:10.1073/pnas.1706814114.
@article{osti_1376517,
title = {Interface-induced multiferroism by design in complex oxide superlattices},
author = {Guo, Hangwen and Wang, Zhen and Dong, Shuai and Ghosh, Saurabh and Saghayezhian, Mohammad and Chen, Lina and Weng, Yakui and Herklotz, Andreas and Ward, Thomas Z. and Jin, Rongying and Pantelides, Sokrates T. and Zhu, Yimei and Zhang, Jiandi and Plummer, E. W.},
abstractNote = {Interfaces between materials present unique opportunities for the discovery of intriguing quantum phenomena. Here, we explore the possibility that, in the case of superlattices, if one of the layers is made ultrathin, unexpected properties can be induced between the two bracketing interfaces. We pursue this objective by combining advanced growth and characterization techniques with theoretical calculations. Using prototype La2/3Sr1/3MnO3 (LSMO)/BaTiO3 (BTO) superlattices, we observe a structural evolution in the LSMO layers as a function of thickness. Atomic-resolution EM and spectroscopy reveal an unusual polar structure phase in ultrathin LSMO at a critical thickness caused by interfacing with the adjacent BTO layers, which is confirmed by first principles calculations. Most important is the fact that this polar phase is accompanied by reemergent ferromagnetism, making this system a potential candidate for ultrathin ferroelectrics with ferromagnetic ordering. Monte Carlo simulations illustrate the important role of spin–lattice coupling in LSMO. These results open up a conceptually intriguing recipe for developing functional ultrathin materials via interface-induced spin–lattice coupling.},
doi = {10.1073/pnas.1706814114},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
number = 26,
volume = 114,
place = {United States},
year = 2017,
month = 5
}
  • Interfaces between materials present unique opportunities for the discovery of intriguing quantum phenomena. Here we explore the possibility that, in the case of superlattices, if one of the layers is made ultrathin, unexpected properties can be induced between the two bracketing interfaces. We pursue this objective by combining advanced growth and characterization techniques with theoretical calculations. Using prototype La 2/3Sr 1/3MnO 3/BaTiO 3 (LSMO/BTO) superlattices, we observe a structural evolution in the LSMO layers as a function of thickness. Atomic-resolution electron microscopy and spectroscopy reveal an unusual polar structure phase in ultrathin LSMO at a critical thickness due to interfacingmore » with the adjacent BTO layers, which is confirmed by first-principles calculations. Most important is the fact that this polar phase is accompanied by re-emergent ferromagnetism, making this system a potential candidate for ultrathin ferroelectrics with ferromagnetic ordering. Monte-Carlo simulations illustrate the important role of spin-lattice coupling in LSMO. The present results open up a conceptually intriguing recipe for developing novel functional ultrathin materials via interface-induced spin-lattice coupling.« less
  • Epitaxial interfaces and superlattices comprised of polar and non-polar perovskite oxides have generated a good deal of interest because of the variety of novel properties they possess. In this work, we examine superlattices comprised of SrTiO3 (STO) and LaCrO3 (LCO) layers; we demonstrate that the differing band alignment of the polar LCO layer and the non-polar STO layer produces a ferroelectric phase transition throughout the STO layers of the superlattice. Through x-ray absorption near edge spectroscopy and aberration-corrected scanning transmission electron microscopy we show that the Ti cations are displaced off-center in the TiO6 octahedra along the superlattice growth direction.more » We also demonstrate that a built-in potential gradient exists within the STO and LCO layers via in situ x-ray photoelectron spectroscopy measurements. Density functional theory models of the system are in excellent agreement with these results, predicting both the ferroelectric octahedral distortion and the built-in electric field. These results represent a new avenue for research in perovskite superlattices, as two non-ferroelectric phases are shown to induce a bulk ferroelectric response due to interfacial phenomena.« less
  • Epitaxial interfaces and superlattices comprised of polar and non-polar perovskite oxides have generated a good deal of interest because of the variety of novel properties they possess. In this work, we examine superlattices comprised of SrTiO3 (STO) and LaCrO3 (LCO) layers; we demonstrate that the differing band alignment of the polar LCO layer and the non-polar STO layer produces a ferroelectric phase transition throughout the STO layers of the superlattice. Through x-ray absorption near edge spectroscopy and aberration-corrected scanning transmission electron microscopy we show that the Ti cations are displaced off-center in the TiO6 octahedra along the superlattice growth direction.more » We also demonstrate that a built-in potential gradient exists within the STO and LCO layers via in situ x-ray photoelectron spectroscopy measurements. Density functional theory models of the system are in excellent agreement with these results, predicting both the ferroelectric octahedral distortion and the built-in electric field. These results represent a new avenue for research in perovskite superlattices, as two non-ferroelectric phases are shown to induce a bulk ferroelectric response due to interfacial phenomena.« less
  • In ABO 3 perovskites, oxygen octahedron rotations are common structural distortions that can promote large ferroelectricity in BiFeO 3 with an R3c structure [1] but suppress ferroelectricity in CaTiO 3 with a Pbnm symmetry [2]. For many CaTiO3-like perovskites, the BiFeO 3 structure is a metastable phase. Here, we report the stabilization of the highly polar BiFeO 3-like phase of CaTiO 3 in a BaTiO 3/CaTiO 3 superlattice grown on a SrTiO 3 substrate. The stabilization is realized by a reconstruction of oxygen octahedron rotations at the interface from the pattern of nonpolar bulk CaTiO 3 to a different patternmore » that is characteristic of a BiFeO 3 phase. The reconstruction is interpreted through a combination of amplitude-contrast sub-0.1-nm high-resolution transmission electron microscopy and first-principles theories of the structure, energetics, and polarization of the superlattice and its constituents. We further predict a number of new artificial ferroelectric materials demonstrating that nonpolar perovskites can be turned into ferroelectrics via this interface mechanism. Therefore, a large number of perovskites with the CaTiO 3 structure type, which include many magnetic representatives, are now good candidates as novel highly polar multiferroic materials [3].« less