First principle calculation of metal superlattice considering intermixing

Abstract

The first principle calculations have been performed for metal superlattices with and without interfacial mixing, and the stability of abrupt interfaces in Co/Cu and Co/Pd superlattices was discussed. The electronic structures of Co(n)Cu(n) and Co(n)Pd(n) superlattices (n = 2, 3, the number of atomic layers) with fcc (face centered cubic) (001) stacking have been calculated using the Linear Muffin-Tin Orbital method in the Atomic Sphere Approximation (LMTO-ASA). In the Co/Cu superlattice with mixing, some Co atoms are exchanged for Cu atoms at interfaces and are surrounded with many neighboring Cu atoms. The Local Density Of States (LDOS) at these sites have been calculated. It was found that the calculated energy at the Co sites in the Co/Cu superlattices with mixing was higher than that in the Co/Cu superlattices without mixing. The energy at the Cu sites in the above superlattice with mixing was found to be almost the same as that of the superlattice without mixing. In the Co/Pd superlattice with mixing, the behavior of Pd atoms was found to be as the same as that of Co atoms in the Co/Cu superlattice. It was found that the spin polarization at the Pd sites in the Co/Pd superlattice with mixing was larger than that in the Co/Pd superlattice without mixing.

界面混合のある場合とない場合について、金属超格子に対して第一原理計算を行い、またCo/CuおよびCo/Pd超格子における急峻界面の安定性を論じた。Fcc(面心立方)多層構造(001)を有するCo(n)Cu(n)およびCo(n)Pd(n)超格子(nは2、3、原子層数)の電子構造を、原子球近似における線形マフィン-ティン軌道法(LMTO-ASA)を用いて計算した。界面混合のあるCo/Cu超格子の場合、いくらかのCo原子は界面でCu原子と交換されて、多数の隣接するCu原子に囲まれる。これらサイトの局所状態密度(LDOS)を計算した。界面混合のあるCo/Cu超格子内のCoサイトにおけるエネルギー計算値は、界面混合のないCo/Cu超格子内のエネルギー値よりも高いことが分かった。混合のある上記超格子内のCuサイトのエネルギーは界面混合のない超格子のエネルギー値とほぼ同じであることが分かった。界面混合のあるCo/Pd超格子の場合、Pd原子の挙動はCo/Cu超格子におけるCo原子の挙動と同じであることが分かった。界面混合のあるCo/Pd超格子内のPdサイトにおけるスピン分極は、界面混合のないCo/Pd超格子内のスピン分極より大きいことが分かった。