Magnetic properties of Co and Ni substituted ε-Fe3N nanoparticles

In the present work, the nanostructured pseudo-binary epsilon-Fe3-x Co (x) N and epsilon-Fe3-x Ni (x) N (x = 0.0-0.8) systems (10-20 nm) are studied in detail for their intrinsic magnetic properties. These systems are indexed based on the hexagonal epsilon-Fe3N phase with the space group P6(3)/mmc. However, for the cobalt containing samples, x = 0.4-0.8, a mixture of hexagonal epsilon-Fe3-x Co (x) N and bcc alpha-Fe phases are formed and for the nickel containing systems, x = 0.5-0.8, small amount of cubic gamma'-Fe4-y Ni (y) N is precipitated and these facts are supported by X-ray diffraction and Fe-57 Mossbauer spectroscopy studies. Mossbauer studies also confirm the random occupation of the substituent elements and the superparamagnetic nature of these particles. The intrinsic magnetic properties (sigma(s), T-c) are observed to vary with the Co and Ni contents. The low temperature magnetic properties are dominated by exchange bias phenomena and spin-glass like ordering, for these compositions.