Geometry of a tunnel junction within a one-dimensional tight-binding model. The open circles denote atoms in the leads and the solid circles denote atoms in the insulating barrier. Vertical positions of the atoms reflect the on-site atomic energies. Parameters of the model are described in text.
Contour plot of the interface DOS, , as a function of energy and interface bonding strength for the tight-binding model described in the text. The interface atom level is . An imaginary part of 0.001 was added to to resolve the localized surface states emerging from the continuum at large . The contour lines correspond to values starting at 0.05 and increasing with the step of 0.05. The vertical lines at show the bulk band edges. The gray level of shading increases with the surface DOS value.
Plots of the interface DOS in a quarter of the surface Brillouin zone for the 3D model. The parameter is equal to 1 in panel (a) and 1.5 in panel (b). The Fermi level is . The top left corner of each panel shows for ; the bottom right corner, for . The gray contrast increases with the interface DOS value. The white color corresponds to zero ; the black color to 0.5 (a) and to 0.3 (b).
Results of first-principles calculations for Co(111)/vacuum/Al MTJs. (a) Clean Co surface and (b) Co surface with an adsorbed O monolayer. Each figure shows the interface Brillouin zone split in four sections. The top left (right) section displays the majority-spin (minority-spin) -resolved DOS at the surface layer of Co in (a) and for the O layer in (b). The bottom left (right) section shows the majority-spin (minority-spin) -resolved conductance for the given MTJ. The gray level varies from white (zero value) to black (value shown next to each frame section). The units are for DOS and for the conductances.
Interfacial structure for model 1 (a and b) and model 2 (c and d) of the MTJ. Panels (a) and (c) show “front” views from a direction normal to the threefold axis; panels (b) and (d) show “top” views along the threefold axis. There are two types of Co and O atoms at the interface for model 2: three O(I) atoms, one O(II) atom, one Co(I) atom, and three Co(II) atoms per unit cell.
Local densities of states for interfacial atoms in model 2 for majority (top panels) and minority (bottom panels) spins. In each figure, top half shows the majority-spin DOS, and bottom half, the minority-spin DOS per atom. The vertical line denotes the position of the Fermi level.
Same as in Fig. 4, but for MTJs. (a) model 1 and (b) model 2. The DOS in top sections is shown for the interface layer of Co in (a) and for the O(II) atom in (b).
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