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Crystal structure of (001) EuO epitaxially grown on (110) depicting the rotation of the EuO unit cell (above) with respect to the pseudocubic lattice (below).
XRD scans from a thick EuO film grown on (110) at approximately and . (a) scan. (b) Azimuthal scan of the 111 EuO diffraction peaks at . aligns the diffraction vector to be perpendicular to the plane of the substrate. corresponds to the in-plane component of the diffraction vector aligned parallel to the  direction of the (110) substrate. Together, these XRD scans show that the EuO film is epitaxial, commensurate, and oriented with and .
Each film was grown at approximately for 30 minutes in the absorption-controlled regime with a europium flux of . Below roughly , the EuO films remain phase pure and additional oxygen reacts with excess europium, increasing the growth rate. At roughly , the europium and oxygen fluxes are matched and increasing results in the formation of impurity phases (first and then ) containing higher oxidation states of europium.
(a) Rocking curves from the 002 EuO peaks of films with different thicknesses and the 220 peak of a substrate. Two superimposed peak shapes near indicate film relaxation through misfit dislocations. The peak intensities are normalized and shifted relative to one another for clarity. (b) FWHM of the 002 EuO film peak as a function of the film thickness. Narrow FWHMs comparable to that of the 220 peak of the substrates are maintained for EuO film thicknesses below . The FWHM begins to broaden beyond this thickness.
Zero-field temperature dependence of the magnetic moment of a thick, commensurately strained EuO film grown on (110) . The onset of ferromagnetism occurs at 69 K. At 5 K, the magnetic hysteresis (inset) shows ferromagnetic behavior with a saturation magnetization of per europium atom, 99.5% of its theoretical maximum.
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