Postgrowth annealing effects on heteroepitaxial MnAs thin films grown on GaAs(001) and Si(001)

摘要

We have carried out postgrowth annealing studies on heteroepitaxial MnAs thin films deposited on GaAs(001) and Si(001) by molecular-beam epitaxy. Before annealing, a paramagnetic behavior is exhibited for MnAs/Si(001), whereas a ferromagnetic behavior is observed for MnAs/GaAs(001). The paramagnetic β-MnAs phase domains of the as-grown MnAs/GaAs(001) sample disappear completely after postgrowth annealing. Surprisingly, after postgrowth annealing, the crystal orientation of the MnAs/Si(001) film changes, and is accompanied by a shift from paramagnetic to ferromagnetic behavior. We attribute these observations to relaxation of the biaxial strain associated with the substrates.