  Using ammonia as nitrogen source for molecular beam epitaxy, the GaN-based
diluted magnetic semiconductor Ga1-xMnxN is successfully grown with Mn
concentration up to x~6.8% and with p-type conductivity. The films have
wurtzite structure with substitutional Mn on Ga site in GaN. Magnetization
measurements revealed that Ga1-xMnxN is ferromagnetic at temperatures higher
than room temperature. The ferromagnetic-paramagnetic transition temperature,
Tc, depends on the Mn concentration of the film. At low temperatures, the
magnetization increases with increasing of magnetic field, implying that a
paramagnetic-like phase coexists with ferromagnetic one. Possible explanations
will be proposed for the coexistence of two magnetic phases in the grown films.
