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Title: Orientation Control of Interfacial Magnetism at La 0.67Sr 0.33MnO 3/SrTiO 3 Interfaces

Abstract

Understanding the magnetism at the interface between a ferromagnet and an insulator is essential because the commonly posited magnetic “dead” layer close to an interface can be problematic in magnetic tunnel junctions. Previously, degradation of the magnetic interface was attributed to charge discontinuity across the interface. In this paper, the interfacial magnetism was investigated using three identically prepared La 0.67Sr 0.33MnO 3 (LSMO) thin films grown on different oriented SrTiO 3 (STO) substrates by polarized neutron reflectometry. In all cases the magnetization at the LSMO/STO interface is larger than the film bulk. We show that the interfacial magnetization is largest across the LSMO/STO interfaces with (001) and (111) orientations, which have the largest net charge discontinuities across the interfaces. In contrast, the magnetization of LSMO/STO across the (110) interface, the orientation with no net charge discontinuity, is the smallest of the three orientations. We show that a magnetically degraded interface is not intrinsic to LSMO/STO heterostructures. Finally, the approach to use different crystallographic orientations provides a means to investigate the influence of charge discontinuity on the interfacial magnetization.

Authors:
ORCiD logo [1];  [1];  [2];  [1]; ORCiD logo [3];  [4]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Instruments and Source Division
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Quantum Condensed Matter Division; Univ. of Tennessee, Knoxville, TN (United States). Dept. of Physics and Astronomy
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); USDOE Laboratory Directed Research and Development (LDRD) Program
OSTI Identifier:
1362256
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Volume: 9; Journal Issue: 22; Journal ID: ISSN 1944-8244
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; charge discontinuity; interfacial magnetization; magnetic “dead” layer; polarized neutron reflectometry

Citation Formats

Guo, Er-Jia, Charlton, Timothy, Ambaye, Haile, Desautels, Ryan D., Lee, Ho Nyung, and Fitzsimmons, Michael R.. Orientation Control of Interfacial Magnetism at La0.67Sr0.33MnO3/SrTiO3 Interfaces. United States: N. p., 2017. Web. doi:10.1021/acsami.7b03252.
Guo, Er-Jia, Charlton, Timothy, Ambaye, Haile, Desautels, Ryan D., Lee, Ho Nyung, & Fitzsimmons, Michael R.. Orientation Control of Interfacial Magnetism at La0.67Sr0.33MnO3/SrTiO3 Interfaces. United States. doi:10.1021/acsami.7b03252.
Guo, Er-Jia, Charlton, Timothy, Ambaye, Haile, Desautels, Ryan D., Lee, Ho Nyung, and Fitzsimmons, Michael R.. 2017. "Orientation Control of Interfacial Magnetism at La0.67Sr0.33MnO3/SrTiO3 Interfaces". United States. doi:10.1021/acsami.7b03252.
@article{osti_1362256,
title = {Orientation Control of Interfacial Magnetism at La0.67Sr0.33MnO3/SrTiO3 Interfaces},
author = {Guo, Er-Jia and Charlton, Timothy and Ambaye, Haile and Desautels, Ryan D. and Lee, Ho Nyung and Fitzsimmons, Michael R.},
abstractNote = {Understanding the magnetism at the interface between a ferromagnet and an insulator is essential because the commonly posited magnetic “dead” layer close to an interface can be problematic in magnetic tunnel junctions. Previously, degradation of the magnetic interface was attributed to charge discontinuity across the interface. In this paper, the interfacial magnetism was investigated using three identically prepared La0.67Sr0.33MnO3 (LSMO) thin films grown on different oriented SrTiO3 (STO) substrates by polarized neutron reflectometry. In all cases the magnetization at the LSMO/STO interface is larger than the film bulk. We show that the interfacial magnetization is largest across the LSMO/STO interfaces with (001) and (111) orientations, which have the largest net charge discontinuities across the interfaces. In contrast, the magnetization of LSMO/STO across the (110) interface, the orientation with no net charge discontinuity, is the smallest of the three orientations. We show that a magnetically degraded interface is not intrinsic to LSMO/STO heterostructures. Finally, the approach to use different crystallographic orientations provides a means to investigate the influence of charge discontinuity on the interfacial magnetization.},
doi = {10.1021/acsami.7b03252},
journal = {ACS Applied Materials and Interfaces},
number = 22,
volume = 9,
place = {United States},
year = 2017,
month = 5
}

Journal Article:
Free Publicly Available Full Text
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Cited by: 3works
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  • The dead-layer behavior, deterioration of the bulk properties in near-interface layers, restricts the applications of many oxide heterostructures. We present the systematic study of the dead-layer in La{sub 0.67}Sr{sub 0.33}MnO{sub 3}/SrTiO{sub 3} grown by ozone-assisted molecular beam epitaxy. Dead-layer behavior is systematically tuned by varying the interfacial doping, while unchanged with varied doping at any other atomic layers. In situ photoemission and low energy electron diffraction measurements suggest intrinsic oxygen vacancies at the surface of ultra-thin La{sub 0.67}Sr{sub 0.33}MnO{sub 3}, which are more concentrated in thinner films. Our results show correlation between interfacial doping, oxygen vacancies, and the dead-layer, whichmore » can be explained by a simplified electrostatic model.« less
  • Epitaxial La{sub 0.67}Ca{sub 0.33}MnO{sub 3}:SrTiO{sub 3} (LCMO:STO) composite thin films have been grown on single crystal LaAlO{sub 3}(001) substrates by a cost effective polymer-assisted deposition method. Both x-ray diffraction and high-resolution transmission electron microscopy confirm the growth of epitaxial films with an epitaxial relationship between the films and the substrates as (002){sub film}||(002){sub sub} and [202]{sub film}||[202]{sub sub}. The transport property measurement shows that the STO phase significantly increases the resistivity and enhances the magnetoresistance (MR) effect of LCMO and moves the metal-insulator transition to lower temperatures. For example, the MR values measured at magnetic fields of 0 and 3more » T are {approx}44.6% at 255 K for LCMO, {approx}94.2% at 125 K for LCMO:3% STO, and {approx}99.4% at 100 K for LCMO:5% STO, respectively.« less
  • The authors have investigated the electrical transport properties of 8 nm thick La{sub 0.67}Ca{sub 0.33}MnO{sub 3} (LCMO) films, sputter deposited on SrTiO{sub 3} (STO), and etched into 5 {mu}m wide bridges by Ar-ion etching. The authors find that even slight overetching of the film leads to conductance of the STO substrate, and asymmetric and nonlinear current-voltage (I-V) characteristics. However, a brief oxygen plasma etch allows full recovery of the insulating character of the substrate. The I-V characteristics of the bridges are then fully linear over a large range of current densities. The authors find colossal magnetoresistance properties typical for strainedmore » LCMO on STO but no signature of nonlinear effects (the so-called electroresistance) connected to electronic inhomogeneites. In the metallic state below 150 K, the highest current densities lead to heating effects and nonlinear I-V characteristics.« less
  • The pulsed laser deposition process of 300 nm thick films of Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}){sub 0.67}-(PbTiO{sub 3}){sub 0.33} on (001)-oriented SrTiO{sub 3} was studied by varying deposition pressure, substrate deposition temperature, laser fluence on the target and target-substrate distance. Perovskite phase pure, (001)-oriented, epitaxial smooth films were obtained in a narrow range of deposition parameters. The ferroelectric and dielectric properties of films fabricated within this parameter range still vary significantly. This shows the sensitivity of the system for growth conditions. The best film has a polarization value close to that expected for a (001) poled, stress free single crystal film.more » All films show deposition conditions dependent variations in the self-bias field. The self-bias is very stable during long cycling for films made at optimum deposition conditions. The piezoelectric coefficients of the films are strongly reduced with respect to bulk single crystal values due to the film clamping. The properties variations are ascribed to changes in the grain boundary properties in which film defects are expected to accumulate. Notably slight off-stoichiometry may cause localized screening charges, affecting specifically the polarization and dielectric constant.« less
  • A La{sub 0.67}Ca{sub 0.33}MnO{sub 3{minus}{delta}} alloy was produced via a low-temperature solid state reaction in a high-energy ball mill. The milled alloy is found to exhibit the paramagnetic-to-ferromagnetic (P{endash}F) transition at 150 K. However, the widely reported insulator-to-metal (I{endash}M) transition that usually accompanies the P{endash}F transition is totally suppressed. Anneals at 500{endash}1000&hthinsp;{degree}C in air (t=8&hthinsp;h) are found to lower the resistivity but not restore the I{endash}M transition. The suppression of the I{endash}M transition is attributed to anion defects in the structure that have not been annihilated during heat treatments. Extended x-ray absorption fine structure is employed to track the evolutionmore » of the atomic structure around the Mn cations at various stages of processing. {copyright} {ital 1999 American Institute of Physics.}« less