Variation of intrinsic magnetic parameters of single domain CoN interstitial nitrides synthesized via hexa-ammine cobalt nitrate route

We report the variation of Curie temperature ( T c ) and coercivity ( H c ) of the single domain Co N interstitial materials synthesized via nitridation of the hexa-ammine Cobalt(III) nitrate complex at 673 K. Co N materials crystallize in the fcc cubic structure with unit cell parameter, a = 3.552 A. The X-ray diffraction (XRD) peaks are broader indicating the materials to be nano-structured with crystallite sizes of 5–14 nm. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies confirm the nanocrystalline nature of the materials. TEM images show chain-like clusters indicating dipolar interactions between the particles. Magnetic studies focus on the existence of giant magnetic Co atoms in the Co N lattice that are not influenced by the thermal relaxation. The values of the H c could be tuned with the dimension of the particles. The values of T c of the nitride materials are masked by the onset of the ferromagnetic to superparamagnetic transition at higher temperatures. Thermomagnetic studies show an increasing trend in the Curie temperature, T c , with decrease in particle dimension. This result has been explained qualitatively on the basis of ferromagnetic to superparamagnetic transition and finite size scaling effects.