Mossbauer effect study of copper containing nickel-aluminate ferrite

A series of spinel ferrite system Ni1-xCuxFeAlO4 with (0.0 less than or equal to x less than or equal to 1.0) were prepared, checked by X-ray, and studied with Fe-57 Mossbauer effect spectroscopy in the 77-470 K temperature range. Characteristic spectra of paramagnetic, magnetic, and electronic types for the different compositions have been observed. Cation distribution obtained from spectral analysis revealed an inverse spinel system. Hyperfine parameters at 77 K were found to be temperature and concentration independent. At 293 K the hyperfine field decreases with increasing Cu concentration. Neel point T-N obtained were found to decrease linearly with the compositional parameter x, Debye temperature theta(D) of this ferrite system increases with increasing Cu content. The temperature dependence of the sublattice magnetization sigma(s)(T) obeys a 1/3 power law in the 0.5 < T/T-N < 0.99 temperature range. (C) 2000 Academic Press.