Magnetotransport properties of a room-temperature ferromagnet (Ga, Mn)N

Heavily Mn-doped GaN thin films were fabricated by using solid-state diffusion. The magnetic properties of the samples were determined by Hall effect measurements and by using a superconducting quantum interference device. The results show ferromagnetic behavior even above room temperature, the Curie temperature being 330 K. The samples were of n-type and the estimated electron concentration was ≈1×10²⁰ cm^-3. Due to the spin-disorder scattering, a negative magnetoresistance was observed and it was largest at Curie temperature. The measured sheet resistance versus temperature could also be explained by the spin disorder scattering model for ferromagnetic metals. From the measurement results, the value of the exchange interaction parameter between the electron spins and the magnetic moments of the Mn atoms was estimated to be about 1 eV. The material properties were studied also by using secondary ion mass spectroscopy and X-ray diffraction, which showed some segregation of Ga_xMn_y.