Tunneling Anisotropic Magnetoresistance Driven by Resonant Surface States: First-Principles Calculations on an Fe(001) Surface

Fully relativistic first-principles calculations of the Fe(001) surface demonstrate that resonant surface (interface) states may produce sizable tunneling anisotropic magnetoresistance in magnetic tunnel junctions with a single magnetic electrode. The effect is driven by the spin-orbit coupling. It shifts the resonant surface band via the Rashba effect when the magnetization direction changes. We find that spin-flip scattering at the interface is controlled not only by the strength of the spin-orbit coupling, but depends strongly on the intrinsic width of the resonant surface states.

Figure 1

(a–c) Spin-resolved integrated transmission $T_{\sigma {\sigma }^{\prime }}$ for the Fe(001) surface with a Cu counterelectrode as a function of energy. Magnetization is along (a) [100], (b) [110], and (c) [001] directions. The Fermi level is at zero energy. (d) In-plane and out-of-plane TAMR as a function of bias voltage.

Figure 2

Spin components of the DOS $N_{\sigma }$ at the Fe(001) surface monolayer and the transmission functions $T_{\sigma {\sigma }^{\prime }}$ for the Fe(001) surface with a Cu counterelectrode at 15 meV below $E_F$. Figures are resolved by ${\mathbf{k}}_{\parallel }$ with abscissa along [100] and ordinate along [010]. The left six panels correspond to the magnetization normal to the surface (labeled by superscript $\perp$), and the right half to the in-plane magnetization aligned along [100] (labeled by superscript $\parallel$). Some panels are given in a logarithmic scale.

Figure 3

Spin-flip transmission $T_{\uparrow \downarrow }$ for magnetization along (a) [100] (in-plane) and (b) [001] (out-of-plane), at $-0.102\mathrm{meV}$.