skip to main content
DOE PAGES title logo U.S. Department of Energy
Office of Scientific and Technical Information

This content will become publicly available on August 20, 2020

Title: Hard x-ray standing-wave photoemission insights into the structure of an epitaxial Fe/MgO multilayer magnetic tunnel junction

Abstract

The Fe/MgO magnetic tunnel junction is a classic spintronic system, with current importance technologically and interest for future innovation. The key magnetic properties are linked directly to the structure of hard-to-access buried interfaces, and the Fe and MgO components near the surface are unstable when exposed to air, making a deeper probing, nondestructive, in-situ measurement ideal for this system. We have thus applied hard X-ray photoemission spectroscopy (HXPS) and standing-wave (SW) HXPS in the few kilo-electron-volt energy range to probe the structure of an epitaxially grown MgO/Fe superlattice. The superlattice consists of 9 repeats of MgO grown on Fe by magnetron sputtering on an MgO(001) substrate, with a protective Al 2O 3 capping layer. We determine through SW-HXPS that 8 of the 9 repeats are similar and ordered, with a period of 33 ± 4 Å, with the minor presence of FeO at the interfaces and a significantly distorted top bilayer with ca. 3 times the oxidation of the lower layers at the top MgO/Fe interface. There is evidence of asymmetrical oxidation on the top and bottom of the Fe layers. We find agreement with dark-field scanning transmission electron microscope (STEM) and X-ray reflectivity measurements. Through the STEM measurements, wemore » confirm an overall epitaxial stack with dislocations and warping at the interfaces of ca. 5 Å. We also note a distinct difference in the top bilayer, especially MgO, with possible Fe inclusions. Finally, we thus demonstrate that SW-HXPS can be used to probe deep buried interfaces of novel magnetic devices with few-angstrom precision.« less

Authors:
 [1]; ORCiD logo [1];  [2];  [3];  [3]; ORCiD logo [1];  [1];  [4];  [5]; ORCiD logo [6];  [7];  [2];  [1];  [1];  [1];  [1]; ORCiD logo [3]; ORCiD logo [1]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
  3. Uppsala Univ. (Sweden)
  4. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  5. SOLEIL Synchrotron, Saint-Aubin (France)
  6. SOLEIL Synchrotron, Saint-Aubin (France); Sorbonne Univ., Paris (France)
  7. Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
Publication Date:
Research Org.:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; USDOE
OSTI Identifier:
1599806
Alternate Identifier(s):
OSTI ID: 1557909
Grant/Contract Number:  
AC02-05CH11231; SC0014697
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 126; Journal Issue: 7; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE

Citation Formats

Conlon, C. S., Conti, G., Nemšák, S., Palsson, G., Moubah, R., Kuo, C. -T., Gehlmann, M., Ciston, J., Rault, J., Rueff, J. -P., Salmassi, F., Stolte, W., Rattanachata, A., Lin, S. -C., Keqi, A., Saw, A., Hjörvarsson, B., and Fadley, C. S. Hard x-ray standing-wave photoemission insights into the structure of an epitaxial Fe/MgO multilayer magnetic tunnel junction. United States: N. p., 2019. Web. doi:10.1063/1.5089556.
Conlon, C. S., Conti, G., Nemšák, S., Palsson, G., Moubah, R., Kuo, C. -T., Gehlmann, M., Ciston, J., Rault, J., Rueff, J. -P., Salmassi, F., Stolte, W., Rattanachata, A., Lin, S. -C., Keqi, A., Saw, A., Hjörvarsson, B., & Fadley, C. S. Hard x-ray standing-wave photoemission insights into the structure of an epitaxial Fe/MgO multilayer magnetic tunnel junction. United States. doi:10.1063/1.5089556.
Conlon, C. S., Conti, G., Nemšák, S., Palsson, G., Moubah, R., Kuo, C. -T., Gehlmann, M., Ciston, J., Rault, J., Rueff, J. -P., Salmassi, F., Stolte, W., Rattanachata, A., Lin, S. -C., Keqi, A., Saw, A., Hjörvarsson, B., and Fadley, C. S. Tue . "Hard x-ray standing-wave photoemission insights into the structure of an epitaxial Fe/MgO multilayer magnetic tunnel junction". United States. doi:10.1063/1.5089556.
@article{osti_1599806,
title = {Hard x-ray standing-wave photoemission insights into the structure of an epitaxial Fe/MgO multilayer magnetic tunnel junction},
author = {Conlon, C. S. and Conti, G. and Nemšák, S. and Palsson, G. and Moubah, R. and Kuo, C. -T. and Gehlmann, M. and Ciston, J. and Rault, J. and Rueff, J. -P. and Salmassi, F. and Stolte, W. and Rattanachata, A. and Lin, S. -C. and Keqi, A. and Saw, A. and Hjörvarsson, B. and Fadley, C. S.},
abstractNote = {The Fe/MgO magnetic tunnel junction is a classic spintronic system, with current importance technologically and interest for future innovation. The key magnetic properties are linked directly to the structure of hard-to-access buried interfaces, and the Fe and MgO components near the surface are unstable when exposed to air, making a deeper probing, nondestructive, in-situ measurement ideal for this system. We have thus applied hard X-ray photoemission spectroscopy (HXPS) and standing-wave (SW) HXPS in the few kilo-electron-volt energy range to probe the structure of an epitaxially grown MgO/Fe superlattice. The superlattice consists of 9 repeats of MgO grown on Fe by magnetron sputtering on an MgO(001) substrate, with a protective Al2O3 capping layer. We determine through SW-HXPS that 8 of the 9 repeats are similar and ordered, with a period of 33 ± 4 Å, with the minor presence of FeO at the interfaces and a significantly distorted top bilayer with ca. 3 times the oxidation of the lower layers at the top MgO/Fe interface. There is evidence of asymmetrical oxidation on the top and bottom of the Fe layers. We find agreement with dark-field scanning transmission electron microscope (STEM) and X-ray reflectivity measurements. Through the STEM measurements, we confirm an overall epitaxial stack with dislocations and warping at the interfaces of ca. 5 Å. We also note a distinct difference in the top bilayer, especially MgO, with possible Fe inclusions. Finally, we thus demonstrate that SW-HXPS can be used to probe deep buried interfaces of novel magnetic devices with few-angstrom precision.},
doi = {10.1063/1.5089556},
journal = {Journal of Applied Physics},
number = 7,
volume = 126,
place = {United States},
year = {2019},
month = {8}
}

Journal Article:
Free Publicly Available Full Text
This content will become publicly available on August 20, 2020
Publisher's Version of Record

Save / Share:

Works referenced in this record:

Giant Magnetoresistance of (001)Fe/(001)Cr Magnetic Superlattices
journal, November 1988


Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange
journal, March 1989


Oscillations in exchange coupling and magnetoresistance in metallic superlattice structures: Co/Ru, Co/Cr, and Fe/Cr
journal, May 1990


Large magnetoresistance effect in 82Ni-Fe/Al-Al2O3/Co magnetic tunneling junction
journal, July 1991


Magnetoresistance and magnetic properties of NiFe/oxide/Co junctions prepared by magnetron sputtering
journal, November 1994

  • Plaskett, T. S.; Freitas, P. P.; Barradas, N. P.
  • Journal of Applied Physics, Vol. 76, Issue 10
  • DOI: 10.1063/1.358319

Theory of tunneling magnetoresistance of an epitaxial Fe/MgO/Fe(001) junction
journal, May 2001


Spin-dependent tunneling conductance of Fe | MgO | Fe sandwiches
journal, January 2001


Large magnetoresistance in Fe/MgO/FeCo(001) epitaxial tunnel junctions on GaAs(001)
journal, September 2001

  • Bowen, M.; Cros, V.; Petroff, F.
  • Applied Physics Letters, Vol. 79, Issue 11
  • DOI: 10.1063/1.1404125

Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers
journal, October 2004

  • Parkin, Stuart S. P.; Kaiser, Christian; Panchula, Alex
  • Nature Materials, Vol. 3, Issue 12
  • DOI: 10.1038/nmat1256

Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions
journal, October 2004

  • Yuasa, Shinji; Nagahama, Taro; Fukushima, Akio
  • Nature Materials, Vol. 3, Issue 12
  • DOI: 10.1038/nmat1257

Tunnel magnetoresistance of 604% at 300K by suppression of Ta diffusion in CoFeB∕MgO∕CoFeB pseudo-spin-valves annealed at high temperature
journal, August 2008

  • Ikeda, S.; Hayakawa, J.; Ashizawa, Y.
  • Applied Physics Letters, Vol. 93, Issue 8
  • DOI: 10.1063/1.2976435

Tunneling Anisotropic Magnetoresistance in Fe Nanoparticles Embedded in MgO Matrix
journal, March 2016


Discrete Layer-by-Layer Magnetic Switching in Fe / MgO ( 001 ) Superlattices
journal, April 2016


First-principles study of the Fe | MgO(0 0 1) interface: magnetic anisotropy
journal, March 2016


Enhanced magnetoresistance by monoatomic roughness in epitaxial Fe/MgO/Fe tunnel junctions
journal, May 2015


Dependence of magnetic anisotropy on MgO thickness and buffer layer in Co 20 Fe 60 B 20 -MgO structure
journal, April 2011

  • Yamanouchi, M.; Koizumi, R.; Ikeda, S.
  • Journal of Applied Physics, Vol. 109, Issue 7
  • DOI: 10.1063/1.3554204

Disturbance of Tunneling Coherence by Oxygen Vacancy in Epitaxial Fe / MgO / Fe Magnetic Tunnel Junctions
journal, June 2008


Effect of structural relaxation and oxidation conditions on interlayer exchange coupling in Fe|MgO|Fe tunnel junctions
journal, June 2010

  • Yang, H. X.; Chshiev, M.; Kalitsov, A.
  • Applied Physics Letters, Vol. 96, Issue 26
  • DOI: 10.1063/1.3459148

Exchange bias of the interface spin system at the Fe/MgO interface
journal, June 2013


Oxygen-Induced Symmetrization and Structural Coherency in Fe / MgO / Fe ( 001 ) Magnetic Tunnel Junctions
journal, October 2005


Structural coherence and layer perfection in Fe/MgO multilayers
journal, January 2008


Observation of boron diffusion in an annealed Ta/CoFeB/MgO magnetic tunnel junction with standing-wave hard x-ray photoemission
journal, November 2012

  • Greer, A. A.; Gray, A. X.; Kanai, S.
  • Applied Physics Letters, Vol. 101, Issue 20
  • DOI: 10.1063/1.4766351

Towards sub-nanometer real-space observation of spin and orbital magnetism at the Fe/MgO interface
journal, March 2017

  • Thersleff, Thomas; Muto, Shunsuke; Werwiński, Mirosław
  • Scientific Reports, Vol. 7, Issue 1
  • DOI: 10.1038/srep44802

Advances in nanomagnetism via X-ray techniques
journal, December 2006

  • Srajer, G.; Lewis, L. H.; Bader, S. D.
  • Journal of Magnetism and Magnetic Materials, Vol. 307, Issue 1
  • DOI: 10.1016/j.jmmm.2006.06.033

Spectroscopic Characterization of Buried Interfaces Using Soft X‐ray Standing Waves
journal, May 2004


Depth Profiling Charge Accumulation from a Ferroelectric into a Doped Mott Insulator
journal, March 2015


Simulation of electron spectra for surface analysis (SESSA): a novel software tool for quantitative Auger-electron spectroscopy and X-ray photoelectron spectroscopy
journal, January 2005

  • Smekal, Werner; Werner, Wolfgang S. M.; Powell, Cedric J.
  • Surface and Interface Analysis, Vol. 37, Issue 11
  • DOI: 10.1002/sia.2097

Calculations of electron inelastic mean free paths. V. Data for 14 organic compounds over the 50-2000 eV range
journal, March 1994

  • Tanuma, S.; Powell, C. J.; Penn, D. R.
  • Surface and Interface Analysis, Vol. 21, Issue 3
  • DOI: 10.1002/sia.740210302

The GALAXIES beamline at the SOLEIL synchrotron: inelastic X-ray scattering and photoelectron spectroscopy in the hard X-ray range
journal, January 2015

  • Rueff, J. -P.; Ablett, J. M.; Céolin, D.
  • Journal of Synchrotron Radiation, Vol. 22, Issue 1
  • DOI: 10.1107/S160057751402102X

Polarization Dependent Bulk-sensitive Valence Band Photoemission Spectroscopy and Density Functional Theory Calculations: Part I. 3 d Transition Metals
journal, December 2017

  • Ueda, Shigenori; Hamada, Ikutaro
  • Journal of the Physical Society of Japan, Vol. 86, Issue 12
  • DOI: 10.7566/JPSJ.86.124706

Simultaneous determination of composition and thickness of thin iron-oxide films from XPS Fe 2p spectra
journal, July 1996


An Efficient Algorithm for Automatic Structure Optimization in X-ray Standing-Wave Experiments
journal, January 2019

  • Karslıoğlu, Osman; Gehlmann, Mathias; Müller, Juliane
  • Journal of Electron Spectroscopy and Related Phenomena, Vol. 230
  • DOI: 10.1016/j.elspec.2018.10.006

Probing buried interfaces with soft x-ray standing wave spectroscopy: application to the Fe/Cr interface
journal, May 2002

  • Yang, See-Hun; Mun, Bongjin S.; Mannella, Norman
  • Journal of Physics: Condensed Matter, Vol. 14, Issue 23
  • DOI: 10.1088/0953-8984/14/23/102

Point defect clusters in wüstite
journal, January 1990

  • Radler, Michael J.; Cohen, Jerome B.; Faber, John
  • Journal of Physics and Chemistry of Solids, Vol. 51, Issue 3
  • DOI: 10.1016/0022-3697(90)90050-P

Electronic structure of FeO, γ Fe 2 O 3 , and Fe 3 O 4 epitaxial films using high-energy spectroscopies
journal, June 2018


Interferenz von Röntgenstrahlen an dünnen Schichten
journal, January 1931