(Ga,Mn)As as a digital ferromagnetic heterostructure

(Ga,Mn)As digital ferromagnetic heterostructures are grown by incorporating submonolayer planes of MnAs into GaAs using molecular beam epitaxy. Structural and magnetic measurements indicate single-crystalline superlattice structure and ferromagnetic order with Curie temperatures (T-C) up to 50 K. By varying the spacing between neighboring Mn layers, we observe that T-C initially decreases with increasing spacer thickness, followed by a regime with weak dependence on the spacer thickness. The persistence of ferromagnetism for interlayer spacings of at least 200 ML (similar to 560 A) suggests that the individual Mn layers are ferromagnetic. (C) 2000 American Institute of Physics. [S0003-6951(00)03041-2].