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Title: Evolution of the interfacial magnetic anisotropy in MgO/CoFeB/Ta/Ru based multilayers as a function of annealing temperature

Abstract

We report the effect of annealing temperature on the dynamic and static magnetic properties of MgO/CoFeB/Ta/Ru multilayers. Angular resolved ferromagnetic resonance measurement results show that the as-deposited film exhibits in-plane magnetic anisotropy, whereas in the annealed films the magnetic easy-axis is almost along the direction perpendicular to the plane of the layers. The extracted interfacial anisotropy energy, K{sub i}, is maximized at an annealing temperature 225{sup ∘}C, in agreement with the vibrating sample magnetometry results. Although the magnetization is not fully out-of-plane, controlling the degree of the magnetization obliqueness may be advantageous for specific applications such as spin-transfer oscillators.

Authors:
;  [1];  [2]; ; ; ; ; ;  [1];  [3]
  1. Helmholtz-Zentrum Dresden - Rossendorf, Institute of Ion Beam Physics and Materials Research, Bautzner Landstr. 400, 01328 Dresden (Germany)
  2. (Germany)
  3. Singulus Technologies AG, Kahl am Main (Germany)
Publication Date:
OSTI Identifier:
22611573
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Advances; Journal Volume: 6; Journal Issue: 6; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANISOTROPY; ANNEALING; BORON COMPOUNDS; COBALT COMPOUNDS; EVOLUTION; FERROMAGNETIC RESONANCE; FILMS; IRON COMPOUNDS; LAYERS; MAGNESIUM OXIDES; MAGNETIC PROPERTIES; MAGNETIZATION; OSCILLATORS; RUBIDIUM; SPIN; TANTALUM; TERNARY ALLOY SYSTEMS

Citation Formats

Aleksandrov, Yuriy, E-mail: y.aleksandrov@hzdr.de, Kowalska, Ewa, Technische Universität Dresden, D-01062 Dresden, Fowley, Ciarán, Sluka, Volker, Yıldırım, Oğuz, Lindner, Jürgen, Fassbender, Jürgen, Deac, Alina M., and Ocker, Berthold. Evolution of the interfacial magnetic anisotropy in MgO/CoFeB/Ta/Ru based multilayers as a function of annealing temperature. United States: N. p., 2016. Web. doi:10.1063/1.4954809.
Aleksandrov, Yuriy, E-mail: y.aleksandrov@hzdr.de, Kowalska, Ewa, Technische Universität Dresden, D-01062 Dresden, Fowley, Ciarán, Sluka, Volker, Yıldırım, Oğuz, Lindner, Jürgen, Fassbender, Jürgen, Deac, Alina M., & Ocker, Berthold. Evolution of the interfacial magnetic anisotropy in MgO/CoFeB/Ta/Ru based multilayers as a function of annealing temperature. United States. doi:10.1063/1.4954809.
Aleksandrov, Yuriy, E-mail: y.aleksandrov@hzdr.de, Kowalska, Ewa, Technische Universität Dresden, D-01062 Dresden, Fowley, Ciarán, Sluka, Volker, Yıldırım, Oğuz, Lindner, Jürgen, Fassbender, Jürgen, Deac, Alina M., and Ocker, Berthold. 2016. "Evolution of the interfacial magnetic anisotropy in MgO/CoFeB/Ta/Ru based multilayers as a function of annealing temperature". United States. doi:10.1063/1.4954809.
@article{osti_22611573,
title = {Evolution of the interfacial magnetic anisotropy in MgO/CoFeB/Ta/Ru based multilayers as a function of annealing temperature},
author = {Aleksandrov, Yuriy, E-mail: y.aleksandrov@hzdr.de and Kowalska, Ewa and Technische Universität Dresden, D-01062 Dresden and Fowley, Ciarán and Sluka, Volker and Yıldırım, Oğuz and Lindner, Jürgen and Fassbender, Jürgen and Deac, Alina M. and Ocker, Berthold},
abstractNote = {We report the effect of annealing temperature on the dynamic and static magnetic properties of MgO/CoFeB/Ta/Ru multilayers. Angular resolved ferromagnetic resonance measurement results show that the as-deposited film exhibits in-plane magnetic anisotropy, whereas in the annealed films the magnetic easy-axis is almost along the direction perpendicular to the plane of the layers. The extracted interfacial anisotropy energy, K{sub i}, is maximized at an annealing temperature 225{sup ∘}C, in agreement with the vibrating sample magnetometry results. Although the magnetization is not fully out-of-plane, controlling the degree of the magnetization obliqueness may be advantageous for specific applications such as spin-transfer oscillators.},
doi = {10.1063/1.4954809},
journal = {AIP Advances},
number = 6,
volume = 6,
place = {United States},
year = 2016,
month = 6
}
  • We have observed several unexpected phenomena when a trace amount of Fe atoms is deposited onto the CoFeB/MgO interface in Ta/CoFeB/MgO/Ta multilayers. With the nominal thickness of the introduced Fe atoms (t{sub Fe}) varying from 0 to 0.1 Å, the effective magnetic anisotropy energy (K{sub eff}) of annealed multilayers is remarkably enhanced from 1.28 × 10{sup 6 }erg/cm{sup 3} to 2.14 × 10{sup 6 }erg/cm{sup 3}. As t{sub Fe} further increasing, the K{sub eff} decreases and even becomes negative when t{sub Fe} > 1 Å, indicating the change from perpendicular magnetic anisotropy to in-plane magnetic anisotropy. The analysis by X-ray photoelectron spectrometer reveals that the Fe atoms at annealed CoFeB/MgOmore » interface show different electronic structures as t{sub Fe} increasing, which combine with O atoms to form FeO{sub x} (x < 1), Fe{sub 2}O{sub 3}, and Fe{sub 3}O{sub 4}, respectively, leading to modulation of Fe 3d-O 2p orbital hybridization and thus the K{sub eff}. On the other hand, we find that the introduction of Fe atoms also helps to reduce the multilayers' magnetic damping.« less
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  • Evolution of structural and magnetic properties of amorphous Co{sub 68}Fe{sub 14}B{sub 18} thin film with thermal annealing has been studied. Initially, the film exhibits a structural relaxation as evidenced by annihilation of excess free volume and an increase in topological short range order. Annealing at 473 K results in precipitation of primary phase followed by formation of boride phase at a still higher temperature of 598 K. Iron preferentially precipitates out in the primary phase, resulting in the formation of bcc Co{sub 58}Fe{sub 41}. This suggests an affinity of Co towards B. Such affinity between Co and B is evidencedmore » even in the as-deposited film, using hard x-ray photoelectron spectroscopy (HAXPES) measurements. As-deposited film exhibits an in-plane uniaxial magnetic anisotropy which disappears at a temperature well beyond crystallization temperature, suggesting that the origin of anisotropy is mainly a chemical short range order in the system. Variation in the coercivity with thermal annealing can be understood in terms of random anisotropy model. Precise measurement of Fe self-diffusion using neutron reflectivity shows that diffusion length associated with annihilation of excess free volume in the film is about 0.5 nm. This agrees with the length scale of structural fluctuations in amorphous alloys. Secondary ion mass spectrometry measurements show that thermal annealing results in depletion of B in the region of the interface with the substrate, with associated faster Fe diffusion in this region. This faster diffusion of Fe may be a possible cause of preferential crystallization of the film in the interfacial region as seen in some earlier studies.« less
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