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Fe/CoO(001) and Fe/CoO(111) bilayers: Effect of crystal orientation on the exchange bias

E. Młyńczak, B. Matlak, A. Kozioł-Rachwał, J. Gurgul, N. Spiridis, and J. Korecki
Phys. Rev. B 88, 085442 – Published 30 August 2013

Abstract

A comparative study of the structure and magnetism of Fe/CoO(111) and Fe/CoO(001) epitaxial bilayers was performed to investigate the role of uncompensated spins in the exchange bias (EB) phenomenon. Low-energy electron diffraction, x-ray photoelectron spectroscopy, conversion electron Mössbauer spectroscopy (CEMS), and the magneto-optic Kerr effect were used to characterize the structural and magnetic properties of the bilayers. Magnetically compensated and uncompensated CoO films were prepared using molecular beam epitaxy through the evaporation of single Co atomic layers and their subsequent oxidation (layer-by-layer technique) on MgO crystals with (001) and (111) orientations. Two-monolayer-thick 57Fe probes located on top of the oxide films and covered with 56Fe allowed for an analysis of the interfacial chemical and magnetic structure using CEMS. For both structures, submonolayer oxidation of the iron detected at the Fe/CoO interface was found to be accompanied by the formation of a mixed FeCo region. The Fe layers showed fourfold magnetocrystalline anisotropy when grown on CoO(001) and weak uniaxial anisotropy when grown on CoO(111). Although the structural quality and composition of the two structures were comparable, they exhibited distinct EB properties. A hysteresis loop shift as high as 354 Oe at 80 K was obtained for the Fe/CoO(111) bilayer, compared to only 37 Oe for the magnetically compensated Fe/CoO(001).

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  • Received 17 June 2013

DOI:https://doi.org/10.1103/PhysRevB.88.085442

©2013 American Physical Society

Authors & Affiliations

E. Młyńczak1,*, B. Matlak2, A. Kozioł-Rachwał2, J. Gurgul1, N. Spiridis1, and J. Korecki1,2

  • 1Jerzy Haber Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Niezapominajek 8, 30-239 Krakow, Poland
  • 2Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, Poland

  • *Author to whom correspondence should be addressed: ncmlyncz@cyf-kr.edu.pl

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Vol. 88, Iss. 8 — 15 August 2013

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