Ferromagnetic III-V semiconductor films with high transition temperature

The fabrication process of the GaAs-based materials included the deposition of the (Ga,Mn)As alloy at low temperature by conventional solid-source molecular beam epitaxy (MBE) and subsequent thermal annealing. The ferromagnetic and paramagnetic phases are found to coexist in the whole temperature range below Tc. Rapid thermal annealing turns the ferromagnetic (Ga,Mn)As into a paramagnetic matrix. The structural and magnetic properties of granular films prepared by using different annealing recipes have been investigated by X-ray diffraction, superconducting quantum interference device magnetometry, and transmission electron microscopy. The temperature dependence of the lattice parameter a of the nanoclusters also exhibits a significant variation around the bulk MnAs phase transition temperature.