(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. Struct ural and magnetic measurements indicate single-crystalline superlattice str ucture 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 ini tially decreases with increasing spacer thickness, followed by a regime wit h weak dependence on the spacer thickness. The persistence of ferromagnetis m for interlayer spacings of at least 200 ML (similar to 560 A) suggests th at the individual Mn layers are ferromagnetic. (C) 2000 American Institute of Physics. [S0003-6951(00)03041-2].