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Study of the Verwey Transition of Fe3O4 Films and Fe3O4/MgO Multilayers Grown by Mbe

Published online by Cambridge University Press:  15 February 2011

R. J. M. Van De Veerdonk ,
M. A. M. Gijs ,
P. A. A. Van Der Heijden ,
R. M. Wolf  and
W. J. M. De Jonge
R. J. M. Van De Veerdonk
Affiliation:
Philips Research Laboratories, Prof. Holstlaan 4, 5656 AA Eindhoven, The Netherlands Department of Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
M. A. M. Gijs
Affiliation:
Philips Research Laboratories, Prof. Holstlaan 4, 5656 AA Eindhoven, The Netherlands
P. A. A. Van Der Heijden
Affiliation:
Philips Research Laboratories, Prof. Holstlaan 4, 5656 AA Eindhoven, The Netherlands Department of Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
R. M. Wolf
Affiliation:
Philips Research Laboratories, Prof. Holstlaan 4, 5656 AA Eindhoven, The Netherlands
W. J. M. De Jonge
Affiliation:
Department of Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
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Abstract

Thin magnetite (Fe3O4) films and Fe3O4/MgO multilayers have been epitaxially grown by Molecular Beam Epitaxy (MBE) on MgO(100) and MgAl2O4(100) substrates. The epitaxial growth on MgO(100) substrates, with a slightly larger bulk lattice parameter than that of magnetite, resulted in an in-plane expansion of the magnetite lattice, accompanied by a perpendicular compression. For films grown on MgAl2O4(100), with a smaller lattice parameter, the substrate misfit is relaxed by the incorporation of misfit dislocations at the interface. It is shown that the substrates have a large effect on the magnetic and electronic properties of the films.

The characteristic Verwey transition is shifted towards lower temperatures, broadened, and reduced in amplitude, more so for thinner films. This can not be quantitatively explained by substrate induced stress alone, but is more likely due to a rigid structural coupling between the magnetite film and the cubic lattice of the substrate. Hereby the orthorhombic deformation accompanying the Verwey transition may be supressed.

When growing at reduced oxygen pressure, the length scale for the rigid coupling will be reduced by the introduction of vacancies. This leads to more bulk-like resistivity and Verwey transition characteristics, but also to deviations from stoichiometry, as suggested by magnetization and Ferromagnetic Resonance (FMR) experiments.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 401: Symposium G – Epitaxial Oxide Thin Films II , 1995 , 455
Copyright
Copyright © Materials Research Society 1996

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