不規則構造を有するCo_2(Cr_<1-x>Fe_x)Alを用いた強磁性トンネル接合のTMR特性(薄膜)

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Polycrystalline and single crystalline thin films of Co_2(Cr_<1-x>Fe_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 Co_2FeAl (x=1) electrode demonstrate TMR of 70% and 75% at 5 K, respectively, which is larger than that of 65% at 5 K for Co_<75>Fe_<25>, indicating that the spin polarization for Co_2FeAl is larger than that for Co_<75>Fe_<25>. The TMR for Co_2FeAl with both the A2 and the B2, which is controlled by substrate heating, is almost the same, whereas for Co_2(Cr_<0.4>Fe_<0.6>)Al the TMR increases with increasing the degree of ordering, corresponding to the first-principles calculations.
2006-05-01