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Phys. Rev. B 52, 13450–13458 (1995)

[Issue 18 – 1 November 1995 ]

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Magnetic anisotropies of sputtered Fe films on MgO substrates

Yu. V. Goryunov, N. N. Garif’yanov, G. G. Khaliullin, and I. A. Garifullin

Kazan Physicotechnical Institute of Russian Academy of Sciences, 420029 Kazan, Russian Federation

L. R. Tagirov

Kazan State University, 420008 Kazan, Russian Federation

F. Schreiber, Th. Mühge, and H. Zabel

Institut für Experimentalphysik, Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany

Ferromagnetic resonance (FMR) and superconducting quantum interference device (SQUID) measurements have been used to study the magnetic properties of rf sputtered Fe films on MgO(001) substrates. The dependences of the FMR spectra parameters on the direction of the dc magnetic field turning in the plane of the films were measured in a wide temperature range (20–400 K) for films with thickness L in the range 25–500 Å. The analysis of the angular dependence of the resonance field H₀ allowed us to determine the fourfold cubic anisotropy constant K₁ and the effective magnetization value M_eff. It was found that both values decrease with decreasing L and approach a constant value below a certain thickness. A theory of FMR is outlined demonstrating that for the case of the dc magnetic field lying in a film plane, the anisotropy constant can be interpreted as a combination of a volume anisotropy contribution and a 1/L-dependent contribution from the surface anisotropy up to the thickness L <= 10³ Å. This means that for the experimentally studied thickness range the films may be considered as ``dynamically thin films'' with respect to surface perturbations. Then the peculiar thickness dependence of the K₁ value can be explained assuming that the relaxation of the strain due to the mismatch between film and substrate extends to distances as far as 45 Å from the film-substrate interface. Since our SQUID measurements show that the saturation moment does not depend on the thickness, it is concluded that the thickness dependence of the effective magnetization M_eff is caused by a second-order uniaxial anisotropy arising mainly from the broken symmetry of the crystal field at surfaces and near the edges of interfacial dislocations.

©1995 The American Physical Society

URL: http://link.aps.org/abstract/PRB/v52/p13450
DOI: 10.1103/PhysRevB.52.13450
PACS: 75.30.Gw, 75.50.Bb

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