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Title: Magnetic damping and spin polarization of highly ordered B2 Co{sub 2}FeAl thin films

Abstract

Epitaxial Co{sub 2}FeAl films were synthesized using the Biased Target Ion Beam Deposition technique. Post annealing yielded Co{sub 2}FeAl films with an improved B2 chemical ordering. Both the magnetization and the Gilbert damping parameter were reduced with increased B2 ordering. A low damping parameter, ∼0.002, was attained in B2 ordered Co{sub 2}FeAl films without the presence of the L2{sub 1} Heusler phase, which suggests that the B2 structure is sufficient for providing low damping in Co{sub 2}FeAl. The spin polarization was ∼53% and was insensitive to the chemical ordering.

Authors:
 [1];  [2]; ; ;  [3];  [4];  [1];  [5]
  1. Department of Physics, University of Virginia, Charlottesville, Virginia 22904 (United States)
  2. Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904 (United States)
  3. Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487 (United States)
  4. Naval Research Laboratory, Washington, DC 20375 (United States)
  5. (United States)
Publication Date:
OSTI Identifier:
22314301
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 116; Journal Issue: 7; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ANNEALING; DAMPING; DEPOSITION; EPITAXY; ION BEAMS; MAGNETIZATION; SPIN ORIENTATION; THIN FILMS; YIELDS

Citation Formats

Cui, Yishen, Lu, Jiwei, E-mail: jl5tk@virginia.edu, Schäfer, Sebastian, Khodadadi, Behrouz, Mewes, Tim, Osofsky, Mike, Wolf, Stuart A., and Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904. Magnetic damping and spin polarization of highly ordered B2 Co{sub 2}FeAl thin films. United States: N. p., 2014. Web. doi:10.1063/1.4893235.
Cui, Yishen, Lu, Jiwei, E-mail: jl5tk@virginia.edu, Schäfer, Sebastian, Khodadadi, Behrouz, Mewes, Tim, Osofsky, Mike, Wolf, Stuart A., & Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904. Magnetic damping and spin polarization of highly ordered B2 Co{sub 2}FeAl thin films. United States. doi:10.1063/1.4893235.
Cui, Yishen, Lu, Jiwei, E-mail: jl5tk@virginia.edu, Schäfer, Sebastian, Khodadadi, Behrouz, Mewes, Tim, Osofsky, Mike, Wolf, Stuart A., and Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904. Thu . "Magnetic damping and spin polarization of highly ordered B2 Co{sub 2}FeAl thin films". United States. doi:10.1063/1.4893235.
@article{osti_22314301,
title = {Magnetic damping and spin polarization of highly ordered B2 Co{sub 2}FeAl thin films},
author = {Cui, Yishen and Lu, Jiwei, E-mail: jl5tk@virginia.edu and Schäfer, Sebastian and Khodadadi, Behrouz and Mewes, Tim and Osofsky, Mike and Wolf, Stuart A. and Department of Materials Science and Engineering, University of Virginia, Charlottesville, Virginia 22904},
abstractNote = {Epitaxial Co{sub 2}FeAl films were synthesized using the Biased Target Ion Beam Deposition technique. Post annealing yielded Co{sub 2}FeAl films with an improved B2 chemical ordering. Both the magnetization and the Gilbert damping parameter were reduced with increased B2 ordering. A low damping parameter, ∼0.002, was attained in B2 ordered Co{sub 2}FeAl films without the presence of the L2{sub 1} Heusler phase, which suggests that the B2 structure is sufficient for providing low damping in Co{sub 2}FeAl. The spin polarization was ∼53% and was insensitive to the chemical ordering.},
doi = {10.1063/1.4893235},
journal = {Journal of Applied Physics},
number = 7,
volume = 116,
place = {United States},
year = {Thu Aug 21 00:00:00 EDT 2014},
month = {Thu Aug 21 00:00:00 EDT 2014}
}
  • We report the investigation of structure and magnetic properties of full-Heusler alloy Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} (CFAS) thin films grown on MgO-buffered MgO (001) substrates through magnetron sputtering. It was found that single-crystal CFAS thin films with high degree of L2{sub 1} ordering and sufficiently flat surface could be obtained after postdeposition annealing. All the films show a distinct uniaxial magnetic anisotropy with the easy axis of magnetization along the in-plane [110] direction. These results indicate that the use of the MgO buffer for CFAS is a promising approach for achieving a higher tunnel magnetoresistance ratio, and thus for spintronicsmore » device applications.« less
  • Ferromagnetic Heusler Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} epitaxial thin-films have been fabricated in the L2{sub 1} structure with saturation magnetizations over 1200 emu/cm{sup 3}. Andreev reflection measurements show that the spin polarization is as high as 80% in samples sputtered on unheated MgO (100) substrates and annealed at high temperatures. However, the spin polarization is considerably smaller in samples deposited on heated substrates.
  • B2-ordered Co{sub 2}FeAl films were synthesized using an ion beam deposition tool. A high degree of chemical ordering {approx}81.2% with a low damping parameter ({alpha}) less than 0.004 was obtained in a 50 nm thick film via rapid thermal annealing at 600 Degree-Sign C. The perpendicular magnetic anisotropy (PMA) was optimized in ultra thin Co{sub 2}FeAl films annealed at 350 Degree-Sign C without an external magnetic field. The reduced thickness and annealing temperature to achieve PMA introduced extrinsic factors thus increasing {alpha} significantly. However, the observed damping of Co{sub 2}FeAl films was still lower than that of Co{sub 60}Fe{sub 20}B{submore » 20} films prepared at the same thickness and annealing temperature.« less
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  • Structural and magnetic properties of epitaxial Co{sub 2}FeAl Heusler alloy thin films were investigated. Films were deposited on single crystal MgO (001XS) substrates at room temperature, followed by an annealing process at 600 deg. C. MgO and Cr buffer layers were introduced in order to enhance crystalline quality, and improve magnetic properties. Structural analyses indicate that samples have grown in the B2 ordered epitaxial structure. VSM measures show that the MgO buffered sample displays a magnetization saturation of 1010 {+-} 30 emu/cm{sup 3}, and Cr buffered sample displays a magnetization saturation of 1032 {+-} 40 emu/cm{sup 3}. Damping factor wasmore » studied by strip-line ferromagnetic resonance measures. We observed a maximum value for the MgO buffered sample of about 8.5 x 10{sup -3}, and a minimum value of 3.8 x 10{sup -3} for the Cr buffered one.« less