Effect of interlayer exchange coupling on the curie temperature in Ga1-xMnxAs trilayer structures

We have investigated the effect of interlayer exchange coupling on the Curie temperature of ferromagnetic (FM) layers in Ga1-xMnxAs(Be)/GaAs/Ga1-xMnxAs trilayer structures. The FM layers in the trilayers contained the same concentration of Mn (x approximate to 0.046). but the top ferromagnetic layer was additionally doped with Be. For this x the Curie temperature observed on a control single-layer sample of Be-doped Ga0.954Mn0.046As is lower than that of an undoped sample. However, in the case of trilayers. we observed that the Curie temperature of the Ga0.954Mn0.046As(Be) layer increased with decreasing thickness of the GaAs spacer separating the two FM layers. This increase in Curie temperature is due to the exchange coupling between the ferromagnetic layers mediated by the spin-polarized free carriers (holes) through the thin insulating spacer.