Influence of the Pt thickness on the structural and magnetic properties of epitaxial Fe/Pt bilayers

Magnetization Reversal and Dynamics in Epitaxial Fe/Pt Spintronic Bilayers Stimulated by Interfacial Fe3O4 Nanoparticles

“…The MgO/Fe interface is not planar but comprises irregular steps of two to five monolayers height, forming multilevel (100) terraces, as shown in Figure 1 a. The Fe layer is epitaxially grown on MgO by a 45° in-plane rotation (Bain orientation), and the resulting lattice mismatch is effectively accommodated by misfit dislocations [ 23 ]. When viewed along the [011]MgO/[001]Fe projection direction as in Figure 1 , the extra half-planes of misfit dislocations are inclined along the <110> Fe directions, as shown in the Bragg filtered image of Figure 1 b. Misfit dislocations bend at the step edges of the MgO/Fe terraces, becoming threading dislocations that propagate along the Fe layer and terminate at the Fe/Pt interface.…”

“…Previous studies have shown that annealing of the MgO substrate at temperatures ranging from 500 to 650 °C results in a smooth and atomically flat surface [ 23 , 24 , 25 , 26 , 27 ]. Hence, the occurrence of uneven terraces at the MgO/Fe is attributed to a local disordering of the MgO surface, due to the elevated growth temperature and the subsequent annealing of the Fe layer that favors Mg outdiffusion [ 24 , 25 , 26 , 27 ].…”

“…The Fe +2 /Fe +3 ratio was calculated by the relative sensitivity factors and the corresponding peak-area, at ≃ 0.476, which along with the presence of the two oxidation states, pinpoints the formation of a near-stoichiometric Fe 3 O 4 structure (0.5 for stoichiometric [ 39 , 40 ]). The formation of a second contribution, centered at 707.7 eV, presages the bimetallic spin interactions at the Fe/Pt interface [ 23 , 41 ], providing hints of a noteworthy rough interface, as observed in the HRTEM images. An average quantification of Fe - 2p peaks was performed at the oxidized interface area, by simulations adjusting each ionic state peak area to its concentration in the metallic structure.…”

“…In Figure 5 a, one can see two-step hysteresis loops at different in-plane angles, as indicated, where we define the switching field values H C1 and H C2 (see Figure 5 a). The appearance of two H C1,2 fields is attributed to the presence of an additional uniaxial magnetic anisotropy overlaying on the cubic fourfold symmetry of the Fe layer as modified by the Pt layer [ 23 ]. Under the assumption of the presence of single-domain states with minimum domain wall nucleation energy at φ = 0°, 90°, 180°, and 270°, the coercive fields H C1 and H C2 can be described by [ 23 , 42 ]: where ε 90° is the 90° domain wall nucleation energy and K u is the uniaxial anisotropy constant.…”

“…The appearance of two H C1,2 fields is attributed to the presence of an additional uniaxial magnetic anisotropy overlaying on the cubic fourfold symmetry of the Fe layer as modified by the Pt layer [ 23 ]. Under the assumption of the presence of single-domain states with minimum domain wall nucleation energy at φ = 0°, 90°, 180°, and 270°, the coercive fields H C1 and H C2 can be described by [ 23 , 42 ]: where ε 90° is the 90° domain wall nucleation energy and K u is the uniaxial anisotropy constant. The excellent quality of the fitting based on Equation (1) is apparent in Figure 5 b, where the coercive fields H C1 and H C2 are plotted against the angle φ .…”