A ferromagnetic resonance study on ultra-thin Fe3O4 layers grown on (001)MgO

Ferromagnetic resonance experiments have been performed on Fe3O4 layers with thicknesses in the range of 1.5-115 nm, which have been grown by molecular beam epitaxy on (001)MgO substrates. For large layer thicknesses, the magnitude as well as the temperature dependence of the magnetic anisotropy resemble the bulk Fe3O4 behavior. At room temperature, the magnetic anisotropy decreases with decreasing Fe3O4-layer thickness and vanishes below 5 nm. Low-temperature FMR experiments show a clear Verwey transition, characteristic for Fe3O4, above layer thicknesses of 5 nm and an anomalous anisotropy behavior at 50 K below 10 nm. (C) 1998 Elsevier Science B.V. All rights reserved.