Figure 1

(Color online) Topographic (constant current) STM images for the ${\mathrm{Fe}}_3{\mathrm{O}}_4\left(001\right)$ surface of the epitaxial magnetite film on $\mathrm{Fe}\left(001\right)∕\mathrm{MgO}\left(001\right)$ (a) and on $\mathrm{MgO}\left(001\right)$ (b). The images are taken at the positive sample bias of about $0.8\mathrm{V}$. For the details of preparation conditions, see text.Reuse & Permissions

Figure 2

(Color) Constant current STM images of the empty (top) and occupied (bottom) states for the ${\mathrm{Fe}}_3{\mathrm{O}}_4\left(001\right)$ surface of the epitaxial magnetite film on $\mathrm{Fe}\left(001\right)∕\mathrm{MgO}\left(001\right)$. Scans from the same areas are shown in columns. The circles in (b) indicate the areas without dimers (I), with $(\surd 2\times \surd 2)R45°–(8.4\times 8.4){\mathrm{\AA }}^2$ (II), and with $(2\times 2)–(12\times 12){\mathrm{\AA }}^2$ (III) square dimer mesh, respectively. The arrow in (c) indicates the line where the sample bias was reversed. The contours of ovals seen in (d) are superimposed on the upper part of (c), and the equivalent positions are marked by corresponding filled and empty contours. Squares labeled with $a$, $b$, and $c$ represent unit cells of $(1\times 1)$, $(\surd 2\times \surd 2)R45°$, and $(2\times 2)$ reconstructions, respectively.Reuse & Permissions

Figure 3

(Color) STM constant current scans taken subsequently from the same area at $-0.73\mathrm{V}$ (a) and $-1.85\mathrm{V}$ (b) sample bias and theoretical STM image of the dimeric $A$ termination at negative $(V_s=-1.7\mathrm{V})$ sample bias (c). Small circles in (a) mark positions of atoms that are equivalent to oval contours in (b). The experimental height profiles along $⟨110⟩$, with colors corresponding to lines marked in (a) and (b), and the theoretical one in gray are shown in the upper right plot. Circle models in (a) and (c) indicate atomic positions on an ideal surface with tetrahedral termination. Green circles represent surface octahedral Fe atoms arranged in rows along $⟨110⟩$, filled white circles are surface tetrahedral Fe atoms in their bulklike positions arranged in the $(1\times 1)$ square lattice, open white circles are surface tetrahedral irons in dimers, yellow circles are subsurface tetrahedral Fe atoms, and small blue circles are oxygen atoms.Reuse & Permissions

Figure 4

(Color online) Constant current STM images of the same surface area for the ${\mathrm{Fe}}_3{\mathrm{O}}_4\left(001\right)$ epitaxial magnetite film on $\mathrm{MgO}\left(001\right)$ taken at a negative (top) and positive (bottom) sample bias.Reuse & Permissions