Valence, exchange interaction, and location of Mn ions in polycrystalline M nx G a1-x N (x≤0.04) VALENCE, EXCHANGE INTERACTION, and LOCATION ⋯ A. FURRER et al.

We present an experimental study for polycrystalline samples of the diluted magnetic semiconductor MnxGa1-xN(x≤0.04) in order to address some of the existing controversial issues. X-ray and neutron diffraction, x-ray absorption near-edge structure, and electron paramagnetic resonance experiments were used to characterize the structural, electronic, and magnetic properties of the samples, and inelastic neutron scattering was employed to determine the magnetic excitations associated with Mn monomers and dimers. Our main conclusions are as follows: (i) The valence of the Mn ions is 2+. (ii) The Mn2+ ions experience a substantial single-ion axial anisotropy with parameter D=0.027(3)meV. (iii) Nearest-neighbor Mn2+ ions are coupled antiferromagnetically. The exchange parameter J=-0.140(7)meV is independent of the Mn content x; i.e., there is no evidence for hole-induced modifications of J towards a potentially high Curie temperature postulated in the literature.