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

We report the variation of Curie temperature (Tc) and coercivity (Hc) of the single domain Cosingle bondN interstitial materials synthesized via nitridation of the hexa-ammine Cobalt(III) nitrate complex at 673 K. Cosingle bondN materials crystallize in the fcc cubic structure with unit cell parameter, a = 3.552 Å. 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 Cosingle bondN lattice that are not influenced by the thermal relaxation. The values of the Hc could be tuned with the dimension of the particles. The values of Tc 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, Tc, with decrease in particle dimension. This result has been explained qualitatively on the basis of ferromagnetic to superparamagnetic transition and finite size scaling effects.