formation, structural, electrical, magnetic and Mössbauer properties of ferrispinels, Cd1−x Ni x Fe2O4

A series of Cd₁₋ₓ Ni ₓ Fe₂O₄ (where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were synthesized by the tartarate precursor method. The formation of these ferrispinels was studied by X-ray powder diffraction, infrared spectroscopy, electrical conductivity, thermoelectric power, magnetic hysteresis, initial magnetic susceptibility and Mössbauer spectroscopy. The temperature variation of the direct current electrical conductivity showed a definite kink (break) in the range 645 to 806 K except for x = 0 and x = 0.2 samples. The kink occurred in each curve (x ≥ 0.4) at a temperature which corresponds to the ferrimagnetic to paramagnetic transition. The thermoelectric power for all samples was negative over the whole range of temperature, indicating that the charge carriers are electrons (i.e. n-type semiconductivity). The compounds with x ≥ 0.4 showed a definite hysteresis loop. The composition dependence of the saturation magnetization (M S) and magnetic moment (n B) up to x = 0.8, has been explained on the basis of the existence of Yafet–Kittel angles on the B-site spins. The Néel's two sublattice model can be applied to the sample with x = 1. The Mössbauer spectra of compounds with x = 0.0 and 0.2 showed a paramagnetic doublet, while x = 0.4 and 0.6 exhibited a relaxation spectrum. The compounds with x ≥ 0.8 exhibited normal Zeeman split sextets at room temperature.