Effect of La3+ Impurity on Magnetic and Electrical Properties of Co-Cu-Cr-Fe Nanoparticles.

In this work a series of Co0.7Cu0.3Cr0.5La(x)Fe1.5-(x)O4 were synthesized via sol-gel auto-combustion technique through the incorporation of La3+ into the raw powders. The structural magnetic and resistivity properties of the synthesized Co-Cu-Cr-La ferrites were investigated. X-ray diffraction data indicated that, after La3+ doping, samples consisted of the main spinel phase in combination with a small amount of a foreign LaFeO3 phase. The addition of La3+ resulted in the reduction of particle size and an increase of porosity of the synthesized samples. The infrared spectra were recorded on the range from 300-800 cm(-1). The two primary bands corresponding to tetrahedral v1 at 595-605 cm(-1) and octahedral v2 at 389-413 cm(-1) were observed. The octahedral site radii increased rapidly with La3+ substitution while the tetrahedral site radii slowly increased. Deviation from the ideal oxygen positional parameter is found to decrease with La3+ substitution. The saturation magnetization of the samples decreased with the amount of La3+ ions doped and the coercivity shows an opposite trend. La3+ substitution affects the hopping between Fe2+ <-> Fe3+, resulted in increase in resistivity.