TY - JOUR
T1 - Exchange-bias in amorphous ferromagnetic and polycrystalline antiferromagnetic bilayers
T2 - Structural study and micromagnetic modeling
AU - Kohn, A.
AU - Dean, J.
AU - Kovacs, A.
AU - Zeltser, A.
AU - Carey, M. J.
AU - Geiger, D.
AU - Hrkac, G.
AU - Schrefl, T.
AU - Allwood, D.
N1 - Funding Information:
This work was funded by the UK Engineering and Physical Sciences Research Council (EP/F016174/1). A. K. acknowledges financial support of the U.K. Royal Academy of Engineering. We thank H. Lichte for imaging on the Tecnai F20 Cs-corr TEM, accessed through the IP3 project of the European Commission, Contract 026019.
PY - 2011/4/15
Y1 - 2011/4/15
N2 - We study the role of the structure of antiferromagnetic polycrystalline metallic films in determining the magnetic properties of an exchange-coupled amorphous ferromagnetic layer. The bilayers are sputter-deposited, highly textured {111} Ir22Mn78 and Co65.5Fe 14.5B20 thin films. We focus on structural characterization of Ir22Mn78 as a function of layer thickness in the range having the strongest influence over the exchange-bias field and training effect. We have used transmission electron microscopy to characterize defects in the form of interface steps and roughness, interdiffusion, twin- and grain-boundaries. Such defects can result in uncompensated magnetic spins in the antiferromagnet, which then contribute to exchange-bias. These experimental results form the basis of a general model, which uses finite element micromagnetic simulations. The model incorporates the experimental structural parameters of the bilayer by implementing a surface integral technique that allows numerical calculations to solve the transition from an amorphous to a granular structure. As a result, a detailed calculation of the underlying magnetic structure within the antiferromagnetic material is achieved. These calculations are in good agreement with micromagnetic imaging using Lorentz transmission electron microscopy and the macro-magnetic properties of these bilayers.
AB - We study the role of the structure of antiferromagnetic polycrystalline metallic films in determining the magnetic properties of an exchange-coupled amorphous ferromagnetic layer. The bilayers are sputter-deposited, highly textured {111} Ir22Mn78 and Co65.5Fe 14.5B20 thin films. We focus on structural characterization of Ir22Mn78 as a function of layer thickness in the range having the strongest influence over the exchange-bias field and training effect. We have used transmission electron microscopy to characterize defects in the form of interface steps and roughness, interdiffusion, twin- and grain-boundaries. Such defects can result in uncompensated magnetic spins in the antiferromagnet, which then contribute to exchange-bias. These experimental results form the basis of a general model, which uses finite element micromagnetic simulations. The model incorporates the experimental structural parameters of the bilayer by implementing a surface integral technique that allows numerical calculations to solve the transition from an amorphous to a granular structure. As a result, a detailed calculation of the underlying magnetic structure within the antiferromagnetic material is achieved. These calculations are in good agreement with micromagnetic imaging using Lorentz transmission electron microscopy and the macro-magnetic properties of these bilayers.
UR - https://www.scopus.com/pages/publications/79955718691
U2 - 10.1063/1.3559261
DO - 10.1063/1.3559261
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AN - SCOPUS:79955718691
SN - 0021-8979
VL - 109
JO - Journal of Applied Physics
JF - Journal of Applied Physics
IS - 8
M1 - 083924
ER -