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

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.

doi:10.1063/1.5089556

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

Journal Article · 20 August 2019 · Journal of Applied Physics

DOI: https://doi.org/10.1063/1.5089556 · OSTI ID:1599806

Conlon, C. S. ^[1];

^[1]; Nemšák, S. ^[2]; Palsson, G. ^[3]; Moubah, R. ^[3];

^[1]; Gehlmann, M. ^[1]; Ciston, J. ^[4]; Rault, J. ^[5];

^[6]; Salmassi, F. ^[7]; Stolte, W. ^[2]; Rattanachata, A. ^[1]; Lin, S. -C. ^[1]; Keqi, A. ^[1]; Saw, A. ^[1];

^[3];

^[1]

Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
Uppsala Univ. (Sweden)
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
SOLEIL Synchrotron, Saint-Aubin (France)
SOLEIL Synchrotron, Saint-Aubin (France); Sorbonne Univ., Paris (France)
Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA

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.

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Research Organization:: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Materials Sciences & Engineering Division; USDOE

Grant/Contract Number:: AC02-05CH11231; SC0014697

OSTI ID:: 1599806

Alternate ID(s):: OSTI ID: 1557909

Journal Information:: Journal of Applied Physics, Vol. 126, Issue 7; ISSN 0021-8979

Publisher:: American Institute of Physics (AIP)Copyright Statement

Country of Publication:: United States

Language:: English

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Cited by: 7 works

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References (41)

Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers Parkin, Stuart S. P.; Kaiser, Christian; Panchula, Alex Nature Materials, Vol. 3, Issue 12 https://doi.org/10.1038/nmat1256	journal	October 2004
Tunneling Anisotropic Magnetoresistance in Fe Nanoparticles Embedded in MgO Matrix Pham, T. V.; Miwa, S.; Suzuki, Y. Journal of Electronic Materials, Vol. 45, Issue 5 https://doi.org/10.1007/s11664-016-4428-2	journal	March 2016
Spin-dependent tunneling conductance of Fe \| MgO \| Fe sandwiches Butler, W. H.; Zhang, X. -G.; Schulthess, T. C. Physical Review B, Vol. 63, Issue 5 https://doi.org/10.1103/PhysRevB.63.054416	journal	January 2001
Disturbance of Tunneling Coherence by Oxygen Vacancy in Epitaxial Fe / MgO / Fe Magnetic Tunnel Junctions Miao, G. X.; Park, Y. J.; Moodera, J. S. Physical Review Letters, Vol. 100, Issue 24 https://doi.org/10.1103/PhysRevLett.100.246803	journal	June 2008
Oxygen-Induced Symmetrization and Structural Coherency in Fe / MgO / Fe ( 001 ) Magnetic Tunnel Junctions Tusche, C.; Meyerheim, H. L.; Jedrecy, N. Physical Review Letters, Vol. 95, Issue 17 https://doi.org/10.1103/PhysRevLett.95.176101	journal	October 2005
First-principles study of the Fe \| MgO(0 0 1) interface: magnetic anisotropy Bose, Thomas; Cuadrado, Ramon; Evans, Richard F. L. Journal of Physics: Condensed Matter, Vol. 28, Issue 15 https://doi.org/10.1088/0953-8984/28/15/156003	journal	March 2016
Oscillations in exchange coupling and magnetoresistance in metallic superlattice structures: Co/Ru, Co/Cr, and Fe/Cr Parkin, S. S. P.; More, N.; Roche, K. P. Physical Review Letters, Vol. 64, Issue 19 https://doi.org/10.1103/PhysRevLett.64.2304	journal	May 1990
Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions Yuasa, Shinji; Nagahama, Taro; Fukushima, Akio Nature Materials, Vol. 3, Issue 12 https://doi.org/10.1038/nmat1257	journal	October 2004
Spectroscopic Characterization of Buried Interfaces Using Soft X‐ray Standing Waves Yang, S. H.; Mun, B. S.; Fadley, C. S. Synchrotron Radiation News, Vol. 17, Issue 3 https://doi.org/10.1080/08940880408603091	journal	May 2004
Point defect clusters in wüstite Radler, Michael J.; Cohen, Jerome B.; Faber, John Journal of Physics and Chemistry of Solids, Vol. 51, Issue 3 https://doi.org/10.1016/0022-3697(90)90050-P	journal	January 1990
Discrete Layer-by-Layer Magnetic Switching in Fe / MgO ( 001 ) Superlattices Moubah, R.; Magnus, F.; Warnatz, T. Physical Review Applied, Vol. 5, Issue 4 https://doi.org/10.1103/PhysRevApplied.5.044011	journal	April 2016
Simultaneous determination of composition and thickness of thin iron-oxide films from XPS Fe 2p spectra Graat, Peter C. J.; Somers, Marcel A. J. Applied Surface Science, Vol. 100-101 https://doi.org/10.1016/0169-4332(96)00252-8	journal	July 1996
Observation of boron diffusion in an annealed Ta/CoFeB/MgO magnetic tunnel junction with standing-wave hard x-ray photoemission Greer, A. A.; Gray, A. X.; Kanai, S. Applied Physics Letters, Vol. 101, Issue 20 https://doi.org/10.1063/1.4766351	journal	November 2012
Determination of layer-resolved composition, magnetization, and electronic structure of an Fe/MgO tunnel junction by standing-wave core and valence photoemission Yang, See-Hun; Balke, Benjamin; Papp, Christian Physical Review B, Vol. 84, Issue 18 https://doi.org/10.1103/PhysRevB.84.184410	journal	November 2011
Enhanced magnetoresistance in layered magnetic structures with antiferromagnetic interlayer exchange Binasch, G.; Grünberg, P.; Saurenbach, F. Physical Review B, Vol. 39, Issue 7 https://doi.org/10.1103/PhysRevB.39.4828	journal	March 1989
Making use of x-ray optical effects in photoelectron-, Auger electron-, and x-ray emission spectroscopies: Total reflection, standing-wave excitation, and resonant effects Yang, S. -H.; Gray, A. X.; Kaiser, A. M. Journal of Applied Physics, Vol. 113, Issue 7 https://doi.org/10.1063/1.4790171	journal	February 2013
Depth Profiling Charge Accumulation from a Ferroelectric into a Doped Mott Insulator Marinova, Maya; Rault, Julien E.; Gloter, Alexandre Nano Letters, Vol. 15, Issue 4 https://doi.org/10.1021/acs.nanolett.5b00104	journal	March 2015
Tunnel magnetoresistance of 604% at 300K by suppression of Ta diffusion in CoFeB∕MgO∕CoFeB pseudo-spin-valves annealed at high temperature Ikeda, S.; Hayakawa, J.; Ashizawa, Y. Applied Physics Letters, Vol. 93, Issue 8 https://doi.org/10.1063/1.2976435	journal	August 2008
Exchange bias of the interface spin system at the Fe/MgO interface Fan, Y.; Smith, K. J.; Lüpke, G. Nature Nanotechnology, Vol. 8, Issue 6 https://doi.org/10.1038/nnano.2013.94	journal	June 2013
An Efficient Algorithm for Automatic Structure Optimization in X-ray Standing-Wave Experiments Karslıoğlu, Osman; Gehlmann, Mathias; Müller, Juliane Journal of Electron Spectroscopy and Related Phenomena, Vol. 230 https://doi.org/10.1016/j.elspec.2018.10.006	journal	January 2019
Giant Magnetoresistance of (001)Fe/(001)Cr Magnetic Superlattices Baibich, M. N.; Broto, J. M.; Fert, A. Physical Review Letters, Vol. 61, Issue 21 https://doi.org/10.1103/PhysRevLett.61.2472	journal	November 1988
Theory of tunneling magnetoresistance of an epitaxial Fe/MgO/Fe(001) junction Mathon, J.; Umerski, A. Physical Review B, Vol. 63, Issue 22 https://doi.org/10.1103/PhysRevB.63.220403	journal	May 2001
Magnetoresistance and magnetic properties of NiFe/oxide/Co junctions prepared by magnetron sputtering Plaskett, T. S.; Freitas, P. P.; Barradas, N. P. Journal of Applied Physics, Vol. 76, Issue 10 https://doi.org/10.1063/1.358319	journal	November 1994
Towards sub-nanometer real-space observation of spin and orbital magnetism at the Fe/MgO interface Thersleff, Thomas; Muto, Shunsuke; Werwiński, Mirosław Scientific Reports, Vol. 7, Issue 1 https://doi.org/10.1038/srep44802	journal	March 2017
Probing buried interfaces with soft x-ray standing wave spectroscopy: application to the Fe/Cr interface Yang, See-Hun; Mun, Bongjin S.; Mannella, Norman Journal of Physics: Condensed Matter, Vol. 14, Issue 23 https://doi.org/10.1088/0953-8984/14/23/102	journal	May 2002
Electronic structure of FeO, γ − Fe 2 O 3 , and Fe 3 O 4 epitaxial films using high-energy spectroscopies Rubio-Zuazo, Juan; Chainani, Ashish; Taguchi, Munetaka Physical Review B, Vol. 97, Issue 23 https://doi.org/10.1103/PhysRevB.97.235148	journal	June 2018
The GALAXIES beamline at the SOLEIL synchrotron: inelastic X-ray scattering and photoelectron spectroscopy in the hard X-ray range Rueff, J. -P.; Ablett, J. M.; Céolin, D. Journal of Synchrotron Radiation, Vol. 22, Issue 1 https://doi.org/10.1107/S160057751402102X	journal	January 2015
Energetic, spatial, and momentum character of the electronic structure at a buried interface: The two-dimensional electron gas between two metal oxides Nemšák, S.; Conti, G.; Gray, A. X. Physical Review B, Vol. 93, Issue 24 https://doi.org/10.1103/PhysRevB.93.245103	journal	June 2016
Large magnetoresistance effect in 82Ni-Fe/Al-Al2O3/Co magnetic tunneling junction Miyazaki, T.; Yaoi, T.; Ishio, S. Journal of Magnetism and Magnetic Materials, Vol. 98, Issue 1-2 https://doi.org/10.1016/0304-8853(91)90417-9	journal	July 1991
Advances in nanomagnetism via X-ray techniques Srajer, G.; Lewis, L. H.; Bader, S. D. Journal of Magnetism and Magnetic Materials, Vol. 307, Issue 1 https://doi.org/10.1016/j.jmmm.2006.06.033	journal	December 2006
Large magnetoresistance in Fe/MgO/FeCo(001) epitaxial tunnel junctions on GaAs(001) Bowen, M.; Cros, V.; Petroff, F. Applied Physics Letters, Vol. 79, Issue 11 https://doi.org/10.1063/1.1404125	journal	September 2001
Dependence of magnetic anisotropy on MgO thickness and buffer layer in Co ₂₀ Fe ₆₀ B ₂₀ -MgO structure Yamanouchi, M.; Koizumi, R.; Ikeda, S. Journal of Applied Physics, Vol. 109, Issue 7 https://doi.org/10.1063/1.3554204	journal	April 2011
Polarization Dependent Bulk-sensitive Valence Band Photoemission Spectroscopy and Density Functional Theory Calculations: Part I. 3 d Transition Metals Ueda, Shigenori; Hamada, Ikutaro Journal of the Physical Society of Japan, Vol. 86, Issue 12 https://doi.org/10.7566/JPSJ.86.124706	journal	December 2017
Enhanced magnetoresistance by monoatomic roughness in epitaxial Fe/MgO/Fe tunnel junctions Duluard, A.; Bellouard, C.; Lu, Y. Physical Review B, Vol. 91, Issue 17 https://doi.org/10.1103/PhysRevB.91.174403	journal	May 2015
Effect of structural relaxation and oxidation conditions on interlayer exchange coupling in Fe\|MgO\|Fe tunnel junctions Yang, H. X.; Chshiev, M.; Kalitsov, A. Applied Physics Letters, Vol. 96, Issue 26 https://doi.org/10.1063/1.3459148	journal	June 2010
Interferenz von Röntgenstrahlen an dünnen Schichten Kiessig, Heinz Annalen der Physik, Vol. 402, Issue 7 https://doi.org/10.1002/andp.19314020702	journal	January 1931
Simulation of electron spectra for surface analysis (SESSA): a novel software tool for quantitative Auger-electron spectroscopy and X-ray photoelectron spectroscopy Smekal, Werner; Werner, Wolfgang S. M.; Powell, Cedric J. Surface and Interface Analysis, Vol. 37, Issue 11 https://doi.org/10.1002/sia.2097	journal	January 2005
Structural coherence and layer perfection in Fe/MgO multilayers Raanaei, Hossein; Lidbaum, Hans; Liebig, Andreas Journal of Physics: Condensed Matter, Vol. 20, Issue 5 https://doi.org/10.1088/0953-8984/20/5/055212	journal	January 2008
Calculations of electron inelastic mean free paths. V. Data for 14 organic compounds over the 50-2000 eV range Tanuma, S.; Powell, C. J.; Penn, D. R. Surface and Interface Analysis, Vol. 21, Issue 3 https://doi.org/10.1002/sia.740210302	journal	March 1994
The Galaxies Beamline at SOLEIL Synchrotron: Inelastic X-ray Scattering and Photoelectron Spectroscopy in the Hard X-ray Range Rueff, J. -P.; Ablett, J. M.; Céolin, D. arXiv https://doi.org/10.48550/arxiv.1806.04058	text	January 2018
An Efficient Algorithm for Automatic Structure Optimization in X-ray Standing-Wave Experiments Karslıoğlu, Osman; Gehlmann, Mathias; Müller, Juliane arXiv https://doi.org/10.48550/arxiv.1807.01780	preprint	January 2018