Magnetic interactions in ε-Fe3N–GaN nanocomposites

Abstract

ε - Fe 3 N – Ga N nanocomposites (∼25nm) are synthesized by the precursor technique according to the ε-Fe3N∕GaN mass ratios of 85∕15, 73∕27, 62∕38, and 54∕46. For ε-Fe3N∕GaN 85∕15 system, single phase ε-Fe2.8Ga0.2N is obtained. For the nanocomposites, GaN forms the shell over the ε-Fe3N core, with a large interface region. The GaN shell protects the ferromagnetic (FM) ε-Fe3N core from surface oxidation effects. The ε-Fe2.8Ga0.2N 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-Fe2.8Ga0.2N system, and the hysteresis loop shift of 19Oe is observed in the positive direction of the cooling field indicating antiparallel/perpendicular alignment of spins across the AF-FM interface. For the ε-Fe3N–GaN nanocomposites, spin-glass-like ordering is observed below 50K 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-Fe3N in the GaN matrix in the core/shell interface region.