Magnetic interactions in ε- Fe3 N-GaN nanocomposites

ε- Fe3 N-GaN nanocomposites (∼25 nm) are synthesized by the precursor technique according to the ε- Fe3 NGaN mass ratios of 8515, 7327, 6238, and 5446. For ε- Fe3 NGaN 8515 system, single phase ε- Fe2.8 Ga0.2 N is obtained. For the nanocomposites, GaN forms the shell over the ε- Fe3 N core, with a large interface region. The GaN shell protects the ferromagnetic (FM) ε- Fe3 N core from surface oxidation effects. The ε- Fe2.8 Ga0.2 N system represents the magnetically diluted system, and significant surface oxidation is observed resulting in antiferromagnetic (AF) oxynitride/oxide surface layer. Exchange bias is observed in ε- Fe2.8 Ga0.2 N system, and the hysteresis loop shift of 19 Oe is observed in the positive direction of the cooling field indicating antiparallel/perpendicular alignment of spins across the AF-FM interface. For the ε- Fe3 N-GaN nanocomposites, spin-glass-like ordering is observed below 50 K in the zero-field cooled curves which is confirmed from relaxation experiments and ac magnetic susceptibility measurements. Spin-glass-like ordering results from the random exchange anisotropy due to the random distribution of ε- Fe3 N in the GaN matrix in the core/shell interface region. © 2007 American Institute of Physics.