Transport and magnetic properties of ferromagnetic GaAs/Mn digital alloys

Magnetic and transport properties of two-dimensional (2D) Mn layers in GaAs Mn digital alloys have been determined as a function of Mn layer coverage. Ferromagnetism was observed in samples having more than 10% Mn in each Mn-containing layer. The Curie temperature showed a strong correlation with the effective spin density in the digital alloy samples. Magnetotransport studies revealed activated behavior hole conductivity consistent with variable range hopping in two dimensions. The general features of magnetoresistance and the anomalous Hall effect are similar to those seen in metallic ferromagnetic GaMnAs. However. the temperature dependence of the observed negative magnetoresistance follows the pattern seen in insulating ferromagnetic GaMnAs. (C) 2002 Published by Elsevier Science B.V.