Low-temperature annealing study of Ga1-xMnxAsGa1-xMnxAs: magnetic properties and Hall effect in pulsed magnetic fields

We have investigated the structural, magnetic and transport properties of a series of epitaxial Ga1-xMnxAsGa1-xMnxAs layers with different Mn contents from x=0.02x=0.02 to x=0.08x=0.08 grown by low-temperature MBE at a thickness of about 40 nm. After growth the samples were submitted to low-temperature resistance-monitored annealing in an oxygen atmosphere. Magnetization measurements show a large enhancement of the Curie temperature and the saturation magnetization. Hall measurements were performed in pulsed magnetic fields up to 50 T, from which the hole densities for all annealed samples have been obtained. We find that hole concentrations determined from the Hall slope at magnetic fields up to 12 T are systematically overestimated.