First-principles calculations of electronic structure and magnetic interactions in diluted magnetic semiconductors

Abstract

Diluted Magnetic Semiconductors (DMS) based on zinc-blende (In, Mn)As and (Ga, Mn)As have been grown by using low temperature molecular beam epitaxy. A semiconductor based ferromagnetic/nonmagnetic multilayer system, (Ga, Mn)As/GaAs, has been found to be ferromagnetic at low temperature. The electronic band-structure calculations have been carried out for a short period magnetic multilayer (MnAs)1(GaAs)3(001) using the Full potential Linearized Augmented Plane Wave (FLAPW) method based on the Local Spin Density Approximation (LSDA). A half metallic behavior has been found in the multilayer system as in the ferromagnetic zinc-blende MnAs and (Ga, Mn)As supercells. It was found that the 4p character of the delocalized valence band carriers (holes) at the As site in the interface region was predominant compared with that at the As site in the non-magnetic layers. It was suggested that the nonmagnetic GaAs layers became the barrier for holes in the MnAs/GaAs heterostructure. The magnetic polarization antiparallel to the Mn moment has been induced at the neighboring As site, while that parallel to the Mn moment has been induced at the Ga site. It was found that the magnetic moments induced at the Ga and the As sites in the nonmagnetic GaAs layers were negligible compared with those at the Ga and the As sites in the interface region.

閃亜鉛鉱型(In, Mn)Asおよび(Ga, Mn)Asを基にした希薄磁性半導体(DMS)を低温分子ビームエピタキシ成長を用いて作製した。半導体系の強磁性/非磁性多層系、(Ga, Mn)As/GaAsは低温では強磁性を示すことが分かった。短周期磁気多層系(MnAs)1(GaAs)3(001)に対して、局所スピン密度近似(LSDA)に基づく全ポテンシャル線形拡大平面波(FLAPW)法を用いて電子バンド構造計算を行った。強磁性閃亜鉛鉱型MnAsおよび(Ga, Mn)Asスーパーセルと同様の半金属的挙動を多層系に見いだした。界面域のAsサイトにおける非局在化価電子帯キャリア(空孔)の4p特性は非磁性層におけるAsサイトの4p特性に比較して支配的であることが分かった。非磁性GaAs層がMnAs/GaAsヘテロ構造体内では空孔に対する障壁となることを示唆した。As隣接サイトにMnモーメントに対し反平行な磁気分極を誘起し、一方でGaサイトにMnモーメントに平行な磁気分極を誘起した。非磁性GaAs層のGaおよびAsサイトで誘起した磁気モーメントは、界面域のGaおよびAsサイトにおける磁気モーメントに比較して極くわずかであることが分かった。