Synthesis and characterization of Al.sup.3+ substituted Ni-Cu-Zn nano ferrites

Ferro spinels with composition Ni.sub.0.2Cu.sub.0.2Zn.sub.0.6Fe.sub.2-xAl.sub.xO.sub.4 (x = 0.0 to 1.0 in steps of 0.2) were synthesized by co-precipitation method, in oxygen atmosphere, from corresponding analytical grade metal sulfates. Thermogravimetric (TG) analysis shows total mass loss around 30% up to 873 K temperature. X-ray diffraction studies confirm all composition with single-phase spinel, cubic structure with crystallite size 11-21 nm range. With increasing trivalent Al.sup.3+ content, lattice parameter 'a' decreases. Infrared spectra shown two major absorption bands, the lower frequency band ν.sub.2 observed in the range 433-463 cm.sup.-1, is assigned to octahedral site and higher frequency band ν.sub.1 observed in the range 565-593 cm.sup.-1, assigned tetrahedral site. The microstructures of the calcinated samples investigated by scanning electron microscopy and transmission electron microscopy indicate ferrite samples are porous in nature. The magnetic properties such as saturation magnetization and magneton number decrease with increasing Al.sup.3+ concentration.