Bulk electron states with $\mathrm{\Delta }$ symmetry in disordered Fe-based alloys for magnetic tunnel junctions

Using first principles methods, we have calculated the changes in the density of states (DOS) with ${\mathrm{\Delta }}_1$ and ${\mathrm{\Delta }}_5$ symmetry, induced by alloying effects in Fe${}_{1-x}$V${}_x$, Fe${}_{1-x}$Cr${}_x$, and Fe${}_{1-x}$Co${}_x$ disordered body centered cubic (bcc) alloys. The Fe${}_{1-x}$V${}_x$ and Fe${}_{1-x}$Cr${}_x$ disordered alloys behave similarly, with ${\mathrm{\Delta }}_1$ Bloch states which remain 100% spin-polarized over the whole range of concentrations. Alloying effects have different consequences in Fe${}_{1-x}$Co${}_x$ alloys for which the minority spin ${\mathrm{\Delta }}_1$-DOS becomes finite at intermediate concentrations. Results on the ${\mathrm{\Delta }}_5$-DOS are also given as a function of the composition for the three bcc alloys. The alloying effects mainly affect the minority spin channel for Fe${}_{1-x}$Co${}_x$ alloys and the majority spin channel for Fe${}_{1-x}$V${}_x$ and Fe${}_{1-x}$Cr${}_x$ alloys. These results could be useful for the interpretation of magnetotransport experiments in magnetic tunnel junctions with a MgO(001) barrier and bcc Fe-based alloy electrodes.

Figure 1

Density of states with ${\mathrm{\Delta }}_1$ symmetry for Fe${}_{1-x}$V${}_x$ alloys with $x=0.0$, 0.3, 0.6, and 1.0. Results for majority and minority spin electrons are, respectively, shown on the left- and right-hand sides.

Figure 2

Density of states with ${\mathrm{\Delta }}_5$ symmetry for Fe${}_{1-x}$V${}_x$ alloys with $x=0.0$, 0.3, 0.6, and 1.0. Results for majority and minority spin electrons are, respectively, shown on the left- and right-hand sides.

Figure 3

Same as in Fig. 1, but for Fe${}_{1-x}$Co${}_x$ alloys.

Figure 4

Same as in Fig. 2, but for Fe${}_{1-x}$Co${}_x$ alloys.

Figure 5

Majority spin (left side) and minority spin (right side) ${\mathrm{\Delta }}_1$-DOS at the Fermi energy for Fe${}_{1-x}$V${}_x$ (full squares), Fe${}_{1-x}$Cr${}_x$ (full circles), and Fe${}_{1-x}$Co${}_x$ alloys (empty circles) versus alloy composition.

Figure 6

Majority spin (left side) and minority spin (right side) ${\mathrm{\Delta }}_5$-DOS at the Fermi energy for Fe${}_{1-x}$V${}_x$ (full squares), Fe${}_{1-x}$Cr${}_x$ (full circles), and Fe${}_{1-x}$Co${}_x$ alloys (empty circles) versus alloy composition.