Preparation and characterization of (111)-oriented Fe3O4 films deposited on sapphire

Abstract

Films of various iron oxides including FeO, Fe3 O4 , and α-Fe2 O3 were formed on the α-Al2 O3 (0001) surface by a reactive vapor deposition method and characterized by x-ray diffraction and conversion electron Mössbauer spectroscopy (CEMS). The formation range for each phase was determined as a function of the substrate temperature (Ts ) and oxygen partial pressure (PO2 ). Typically, the deposition of (111)-oriented epitaxial magnetite films could be performed at low temperatures of Ts =523∼623 K and PO2 =1.0–5.0×10−4 Torr. Good stoichiometry of the as-grown films were confirmed by CEMS, and the Verwey transition was clearly detected by measurements of resistivity and CEMS down to 77 K. However, the large lattice mismatch between the substrate and Fe3 O4 resulted in a columnar particle growth. The initially grown phase on such a mismatched substrate was specifically characterized by depositing the Mössbauer active isotope, 57 Fe, only at the deepest layers. On the other hand, by depositing 57 Fe only in the topmost layers, surface layers of well-crystallized films have been found to be rather stable against oxidation.

Surface and interface properties of epitaxial iron oxide thin films deposited on MgO(001) studied by XPS and Raman spectroscopy

“…Such interfaces are present in new types of magnetic multilayer compounds containing Fe 3 O 4 layers. 2,3 A range of techniques has been used for the production of high-quality magnetite thin films, including reactive molecular beam epitaxy, 4 oxygen-plasma-assisted molecular beam epitaxy 3,5 and pulsed laser deposition. 6 To improve the magnetic properties of the films, epitaxial growth is desirable.…”

Surface chemistry and catalysis on well-defined epitaxial iron-oxide layers

“…Well-ordered epitaxial Fe-oxide films were also obtained by some other techniques. Fe 3 O 4 (100) films were grown on MgO(100) substrates by MBE in oxygen [165,166]and NO 2 [167] atmospheres, several orientations of Fe 3 O 4 and α-Fe 2 O 3 films were grown on different surface planes of Al 2 O 3 and MgO substrates by oxygen-plasma-assisted MBE [168][169][170]. For studying the coupling between magnetic layers, Fe 3 O 4 /NiO [171] and Fe 3 O 4 /CoO [172] superlattices were grown by MBE.…”

Magnetism in nanometer-thick magnetite

“…9 Oxides like magnetite have much more complicated structures and larger unit cells than metal ferromagnets, giving the possibility of tuning their properties to a larger extent, especially given the often observed strong coupling to strain effects. 10,11 Magnetite ultrathin nanostructures have been grown on a variety of substrates, including oxides, [12][13][14][15][16][17][18] semiconductors, [18][19][20][21][22] and metals. [23][24][25][26][27][28] Here we examine the presence of stable ferrimagnetic domains in ultrathin magnetite, a subject with conflicting reports in the literature.…”

“…While some reports state than magnetite films close to 3 nm thick present a well defined magnetic structure, 20,22,23,29,30 others indicate that clear signs of superparamagnetic behavior are observed at the same thickness. 12,[31][32][33][34] We grow 1-nm-thick, micron-wide, magnetite crystals on ruthenium 25 using reactive molecular beam epitaxy (i.e., depositing iron in a background of oxygen) while monitoring the growth in real time by low-energy electron microscopy (LEEM 27 ). We show by imaging their individual magnetization patterns and their x-ray magnetic circular dichroism (XMCD) spectra that they are ferrimagnetic.…”