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Journal of Materials Science

, Volume 50, Issue 1, pp 122–137 | Cite as

Insights into the structural, electronic, and magnetic properties of Fe2−x Ti x O3/Fe2O3 thin films with x = 0.44 grown on Al2O3 (0001)

  • Teresa Dennenwaldt
  • Maike Lübbe
  • Michael Winklhofer
  • Alexander Müller
  • Markus Döblinger
  • Hasan Sadat Nabi
  • Maria Gandman
  • Tzipi Cohen-Hyams
  • Wayne D. Kaplan
  • Wolfgang Moritz
  • Rossitza Pentcheva
  • Christina ScheuEmail author
Original Paper

Abstract

The interface between hematite (α-Fe 2 III O3) and ilmenite (FeIITiO3), a weak ferrimagnet and an antiferromagnet, respectively, has been suggested to be strongly ferrimagnetic due to the formation of a mixed valence layer of Fe2+/Fe3+ (1:1 ratio) caused by compensation of charge mismatch at the chemically abrupt boundary. Here, we report for the first time direct experimental evidence for a chemically distinct layer emerging at heterointerfaces in the hematite—Ti-doped-hematite system. Using molecular beam epitaxy, we have grown thin films (~25 nm thickness) of α-Fe2O3 on α-Al2O3 (0001) substrates, which were capped with a ~25 nm thick Fe2−x Ti x O3 layer (x = 0.44). An additional 3 nm cap of α-Fe2O3 was deposited on top. The films were structurally characterized in situ with surface X-ray diffraction, which showed a partial low index orientation relationship between film and substrate in terms of the [0001] axis and revealed two predominant domains with \( (0001) _{{{\text{Fe}}_{2} {\text{O}}_{3} }} \;||\;(0001) _{{{\text{Al}}_{2} {\text{O}}_{3} }}, \) one with \( [10\bar{1}0]_{{{\text{Fe}}_{2} {\text{O}}_{3} }} \;||\;[10\bar{1}0]_{{{\text{Al}}_{2} {\text{O}}_{3} }}, \) and a twin domain with \( [01\bar{1}0]_{{{\text{Fe}}_{2} {\text{O}}_{3} }} \;||\;\;[10\bar{1}0]_{{{\text{Al}}_{2} {\text{O}}_{3} }}. \) Electron energy loss spectroscopy profiles across the Fe2−x Ti x O3/Fe2O3 interface show that Fe2+/Fe3+ ratios peak right at the interface. This strongly suggests the formation of a chemically distinct interface layer, which might also be magnetically distinct as indicated by the observed magnetic enhancement in the Fe2−x Ti x O3/α-Fe2O3/Al2O3 system compared to the pure α-Fe2O3/Al2O3 system.

Keywords

Magnetite Hematite Ilmenite Orientation Relationship Electron Energy Loss Spectroscopy 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgement

The authors C.S. and A. M. would like to thank the Deutsche Forschungsgemeinschaft (DFG) for financial support via the project SCHE634/12-1 within the priority program SPP1613. R.P., M.W. and W.M. acknowledge the DFG, Grant No PE883/4-1 (ESF EUROMISCI Program, Project MICROMAGN) and STA 1026/2-1. We thank Peter Gille and Renate Enders for their help with the preparation of the α-Al2O3 substrates, Matthias Opel and Rudolf Groß for measurement time on their SQUID magnetometer, and Alexander Gigler for help with the Raman measurements.

Supplementary material

10853_2014_8572_MOESM1_ESM.pdf (140 kb)
Supplementary material 1 (PDF 139 kb)

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Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  • Teresa Dennenwaldt
    • 1
    • 5
  • Maike Lübbe
    • 2
  • Michael Winklhofer
    • 2
  • Alexander Müller
    • 1
    • 5
  • Markus Döblinger
    • 1
  • Hasan Sadat Nabi
    • 2
  • Maria Gandman
    • 3
  • Tzipi Cohen-Hyams
    • 4
  • Wayne D. Kaplan
    • 4
  • Wolfgang Moritz
    • 2
  • Rossitza Pentcheva
    • 2
    • 6
  • Christina Scheu
    • 1
    • 5
    Email author
  1. 1.Department of Chemistry and Center for NanoScienceLudwig-Maximilians-Universität MünchenMunichGermany
  2. 2.Department of Earth and Environmental Sciences and Center for NanoscienceLudwig-Maximilians-Universität MünchenMunichGermany
  3. 3.Department of Materials Science and Engineering 210 Hearst Memorial Mining BuildingUniversity of CaliforniaBerkeleyUSA
  4. 4.Department of Materials Science and EngineeringTechnion – Israel Institute of TechnologyHaifaIsrael
  5. 5.Max-Planck-Institut für EisenforschungDüsseldorfGermany
  6. 6.Faculty of PhysicsUniversity of Duisburg-EssenDuisburgGermany

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