Thin magnetite (Fe304) films and Fe304/MgO multilayers have been epitaxially grown by Molecular Beam Epitaxy (MBE) on MgO(100) and MgA12O4(100) substrates. The epi taxial 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 MgAlsO4(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 ex plained 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.
|Title of host publication||Epitaxial oxide thin films II : Symposium held November 26 - 30, 1995, Boston, Massachusetts|
|Editors||J.S. Speck, D.K. Fork|
|Place of Publication||Pittsburgh|
|Publisher||Materials Research Society|
|Publication status||Published - 1996|
|Event||Epitaxial Oxide Thin Films II, November 26-30, 1995, Boston, MA, USA - Boston, MA, United States|
Duration: 26 Nov 1995 → 30 Nov 1995
|Name||Materials Research Society Symposium Proceedings|
|Conference||Epitaxial Oxide Thin Films II, November 26-30, 1995, Boston, MA, USA|
|Period||26/11/95 → 30/11/95|
|Other||Symposium held at the 1995 MRS Fall Meeting|
Veerdonk, van de, R. J. M., Gijs, M. A. M., Heijden, van der, P. A. A., Wolf, R. M., & Jonge, de, W. J. M. (1996). Study of the Verwey transition of Fe3O4 films and Fe3O4/MgO multilayers grown by MBE. In J. S. Speck, & D. K. Fork (Eds.), Epitaxial oxide thin films II : Symposium held November 26 - 30, 1995, Boston, Massachusetts (pp. 455-460). (Materials Research Society Symposium Proceedings; Vol. 401). Pittsburgh: Materials Research Society.