TMR Properties for magnetic tunnel junctions with a disordered Co₂(Cr_1-xFe_x)Al electrode

Abstract

Polycrystalline and single crystalline thin films of Co₂(Cr_1-xFe_x)Al (x = 0.6, 1) full-Heusler alloys with different disordering were prepared on thermally oxidized Si and MgO(001) substrates, respectively, by the dc magnetron sputtering method. The magnetic tunnel junctions with a polycrystalline and single crystalline B2 type Co₂FeAl (x =1) electrode demonstrate TMR of 70% and 75% at 5 K, respectively, which is larger than that of 65% at 5 K for Co₇₅Fe₂₅, indicating that the spin polarization for Co₂FeAl is larger than that for Co₇₅Fe₂₅. The TMR for Co₂FeAl with both the A2 and the B2, which is controlled by substrate heating, is almost the same, whereas for Co₂(Cr_0.4Fe_0.6)Al the TMR increases with increasing the degree of ordering, corresponding to the first-principles calculations.