Systematic study on the spacer-dependent magnetic properties of Mn δ-doped GaAs/(Ga, Mn)As ferromagnetic heterostructures: from first principles

Abstract

First-principles calculations based on density-functional theory have been performed on the spacer-dependent magnetic properties of δ-doped GaAs/(Ga, Mn)As ferromagnetic heterostructures (DFH). It is found that all the structures show ferromagnetic (FM) alignment as the favoured configuration. Their electronic structures are half-metallic independent of the spacer thickness d. The interlayer exchange coupling (IEC) between two magnetic layers decreases sharply at first with increasing d, then reaches a stationary value at d = 4a0 (a0 is the lattice constant of GaAs), where the FM and antiferromagnetic states become energetically degenerate. The charge density and the strong spin-polarized holes are concentrated mostly in the vicinity of MnAs magnetic layers for all the structures. After the injection of free holes into the system, we confirm the free-hole mediated mechanism for the intralayer exchange coupling and IEC. Furthermore, the injection of holes enhances the intralayer exchange coupling much more than the IEC. From these results, it is definitely shown that the magnetic coupling of DFH can get across a nonmagnetic spacer. It is closely related to the spacer thickness d, and the redistribution of injection holes plays a key role when d is small.