Novel Synthesis and Nanostructure Controlled Magnetic Characteristics of ε-Fe3N and γ'-Ni x Fe4-x N (0.2 aparts per thousandcurrency sign x aparts per thousandcurrency sign 0.8) Nitrides

Nanocrystalline epsilon-Fe3N and gamma'-Ni (x) Fe4-xN (0.2 a parts per thousand currency sign x a parts per thousand currency sign 0.8) nitride materials are synthesized in pure phase via sol-gel-mediated oxide precursors. The materials are characterized using XRD, SEM (EDX), and magnetic measurements. epsilon-Fe3N and gamma'-Ni (x) Fe4-x N (0.2 a parts per thousand currency sign x a parts per thousand currency sign 0.8) materials crystallize in hexagonal and cubic structures, respectively. The lattice parameters are estimated to be a = 4.7812(36) and c = 4.4232(31) for epsilon-Fe3N and in the range of 3.7922(10)-3.7957(3) for various gamma'-Ni (x) Fe4 -xN (0.2 a parts per thousand currency sign x a parts per thousand currency sign 0.8) materials. The values of the lattice parameters show increasing trend up to x = 0.6, showing a peak, and thereafter decreases with the increase in Ni weight percent in gamma'-Ni (x) Fe4-xN (0.2 a parts per thousand currency sign x a parts per thousand currency sign 0.8) materials. The average crystallite sizes are in the range of 31-54 nm and confirm the nanocrystalline nature of the materials. The SEM particle sizes are in the range of 153(7)-250(14) nm. For pure epsilon-Fe3N, the values of saturation magnetization (M (s)) and coercivity (H (c)) are 12 emu/g and 225 Oe, respectively. With the progressive substitution of Ni atoms, hexagonal (epsilon-phase) changes to cubic (gamma'-phase) at the same reaction temperature, which is evident from the increase in M (s) and H (c) values, i.e., in the range of 144-181 emu/g and 76-109 Oe, respectively, for gamma'-Ni (x) Fe4 -xN (0.2 a parts per thousand currency sign x a parts per thousand currency sign 0.8) compounds. The values of the saturation magnetization for gamma'-Ni (x) Fe4 -xN (0.2 a parts per thousand currency sign x a parts per thousand currency sign 0.8) are found to increase with the increase in Ni content in the materials up to the value of x = 0.6 and decrease thereafter. These results have been interpreted in terms of size and shape effects in nanomaterials including lattice strain and surface effects.