Spacer-dependent transport and magnetic properties of digital ferromagnetic heterostructures

We examine the relationship between the transport and magnetic properties of digital ferromagnetic heterostructure superlattices in which 0.5 monolayer MnAs planes alternate with undoped GaAs spacer layers. The data show that as the thickness t of the GaAs spacers increases, charge transport and the Curie temperature both approach their independent-layer limits at comparable values of t. An increase in the per-layer conductivity with decreasing t accompanies a rise in TC. This behavior is consistent with an enhancement of interlayer ferromagnetic interactions by charge coupling across the spacers.