Study of the Verwey transition of Fe{sub 3}O{sub 4} films and Fe{sub 3}O{sub 4}/MgO multilayers grown by MBE

Book · Thu Oct 31 23:00:00 EST 1996

OSTI ID:392197

Gijs, M A.M.; Wolf, R M ^[1]; Jonge, W J.M. de ^[2]

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1. Philips Research Labs., Eindhoven (Netherlands)
2. Eindhoven Univ. of Technology, Eindhoven (Netherlands). Dept. of Physics

Thin magnetite (Fe{sub 3}O{sub 4}) films and Fe{sub 3}O{sub 4}/MgO multilayers have been epitaxially grown by Molecular Beam Epitaxy (MBE) on MgO(100) and MgAl{sub 2}O{sub 4}(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 MgAl{sub 2}O{sub 4}(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 suppressed. 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.

• OSTI ID: 392197
• Report Number(s): CONF-951155--; ISBN 1-55899-304-5
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINATES
COMPOSITE MATERIALS
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
EVAPORATION
EXPERIMENTAL DATA
IRON OXIDES
LATTICE PARAMETERS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MAGNETIC PROPERTIES
MOLECULAR BEAM EPITAXY
OXIDATION
OXYGEN
PARTIAL PRESSURE
PHYSICAL VAPOR DEPOSITION
PRESSURE DEPENDENCE
STOICHIOMETRY
SUBSTRATES
TRANSITION TEMPERATURE