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Structural characterization: (a) Chemical order within crystalline FePt3 (small arrows indicate the direction of the Fe moments, Pt is drawn without arrows). (b) X-ray diffraction of cubic FePt3 along (001) and (002). The difference in (001) intensity determines the degree of chemical order. The dashed lines are Voigt-fits to the data. (c) ϕ-scan along (022). The 90° periodicity indicates the epitaxial growth along the cubic symmetry.
High angle neutron diffraction along the direction of the 2800 Å thick FePt3 thin films with O = 86% (a) and O = 54% (b). Lines are Gaussian fits to the data. (c) Temperature dependence of the integrated AFM peak intensity (the line is a guide to the eye). The dashed line represents the values obtained for a FePt3 order-modulated multilayer. 12
Dark-field TEM images formed with a (001) diffracted beam for the cross sections of FePt3 samples with different chemical order. Bright regions correspond to chemical order, while dark ones represent disordered domains. Arrows in the image for O = 86% indicate the magnetic ordering within the sample's domains.
Magnetic characterization: (a) magnetic hysteresis of the three samples at 10 K after field cooling in 1 T. (b) Exchange bias, determined as a shift of the hysteresis loop from the origin along the field axis. (c) Magnetic coercivity as a function of temperature. (d) AC susceptibility measured from low to high temperatures after field cooling in 1 T. The dashed lines in (b)–(d) represent the values obtained for a FePt3 order-modulated multilayer. 12
Growth temperature (TG ), chemical order parameter (O), chemically ordered grain size (dg ), Néel temperature TN , and exchange bias at 10 K of the three (2800 Å) FePt3 thin films (Magnetic parameter is determined further below in this manuscript).
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