Large tunneling magnetoresistance in GaMnAs/AlAs/GaMnAs ferromagnetic semiconductor tunnel junctions

Abstract

Very large Tunneling Magnetoresistance (TMR) was observed in epitaxially grown Ga(1-x)Mn(x)As/AlAs/Ga(1-x)Mn(x)As ferromagnetic semiconductor tunnel junctions. Large TMR ratios more than 70 percent were obtained in junctions with a very thin (less than or equal to 1.6 nm) AlAs tunnel barrier when the magnetic field was applied along the (100) axis in the film plane. The TMR was found to rapidly decrease with increasing the barrier thickness, which is explained by calculations assuming that the parallel wavevector of carriers is conserved in tunneling.

エピタキシ成長させたGa(1-x)Mn(x)As/AlAs/Ga(1-x)Mn(x)As強磁性半導体トンネル接合において、非常に大きなトンネル磁気抵抗(TMR)を観察した。1.6nm以下の非常に薄いAlAsトンネル障壁により形成される接合では、膜面の(100)軸に沿って磁場をかけると、70%以上という大きなTMR比が得られた。障壁厚を増加すると、TMRは急激に減少した。キャリアの波数ベクトルの平行成分がトンネル時に保存すると仮定した計算によってこの現象は説明できた。